FORENSICS UNDER THE MICROSCOPE
Unproven techniques sway courts, erode justiceBy Flynn McRoberts, Steve Mills and Maurice Possley, Tribune staff reporters.
Tribune researcher Judith Marriott contributed to this report
October 17, 2004
Settling into the witness chair of a Kane County courtroom, Stephen McKasson tutored jurors in a murder trial on the wonders of a rarely used divining tool: lip prints.
The Illinois State Police crime lab examiner told them forensic science accepts that lips have unique creases and he could match the prints found on duct tape at the crime scene to the defendant, Lavelle Davis.
Davis was convicted and sentenced to 45 years. The lip print, one juror in the 1997 trial recalled, "proved that he had actually committed the crime."
There was just one problem: What McKasson asserted about lip prints isn't true.
The story of how an unproven forensic theory helped send a man to prison might seem like a legal curiosity befitting an episode of "CSI: Crime Scene Investigation."
But a Tribune investigation of forensics in the courtroom shows how Davis' conviction exemplifies the questionable science, flawed analysis and shoddy lab practices that sometimes undermine the quest for justice. Long considered unbiased and untainted, crime labs and analysts are facing new scrutiny and tough questions about their accuracy.
At the center of this upheaval is the advent of DNA testing, which has injected a dose of truth serum into other forensic tools. With its dramatic precision, DNA has helped reveal the shaky scientific foundations of everything from fingerprinting to firearm identification, from arson investigation to such exotic methods as bite-mark comparison.
It is difficult, if not impossible, to quantify precisely how many cases have been affected by faulty forensic testimony or poor analytical work, partly because defense attorneys often haven't challenged forensic evidence. Many lack the resources to do so, others assume the science is unassailable, and some simply don't bother.
But the 200 DNA and Death Row exoneration cases nationwide in the last 20 years offer one clue. More than a quarter--55 cases with 66 defendants--involved forensic testing or testimony that was flawed.
The Tribune investigation included hundreds of interviews across the country, an examination of thousands of court documents and an analysis of criminal cases that turned on forensic evidence. Among the findings:
- Fingerprinting is so subjective that the most experienced examiners can make egregious mistakes. This year, in a stunning embarrassment, the FBI was forced to admit it wrongly linked an Oregon lawyer to the Madrid terror bombing case because of an erroneous fingerprint comparison.
- Prosecutors continue to rely on experts who embrace debunked theories about arson. Among the hard-to-kill myths is "crazed glass"--glass lined with a spider web of cracks--which was thought to be evidence of an accelerant until researchers learned it could occur when hot glass is sprayed with water, as in putting out a fire.
- Forensic dentists, who link suspects to bite marks left on crime victims, continue to testify despite having no accepted way to measure their rate of error or the benefit of peer review. DNA testing has shown that even the field's leading practitioners have made false bite-mark matches.
- Scandals at labs from Maryland to Washington state have spotlighted analysts who have incorrectly assessed evidence, hidden test results helpful to defendants and testified falsely in court. The scandals underscore the often-ineffective standards governing crime labs.
Analysts involved in faulty forensic work typically have testified in hundreds of trials, just one indication of how widespread the impact of bad science and bad scientists can be. The lab scandals also have laid bare a more fundamental failure: Experts often express certitude based on an unfounded confidence in their forensic specialty and their ability to practice it.
"I have no problem with forensic science. I have a problem with the impression that's being given that those disciplines ... can make an absolute identification of someone, and that's not the case," said Terrence Kiely, a DePaul University law professor and author of "Forensic Evidence: Science and the Criminal Law."
"It's the white coat-and-resume problem," he added. "They're very, very believable people. And sometimes the jurors will take [their testimony] as a `yes,' where the science can only say it's a `maybe.'"
The explosive popularity of TV shows such as "CSI" has led prosecutors and crime lab directors in recent months to complain that juries and the public have unreasonable confidence in what forensic analysts can do and how quickly they can do it.
An examination of forensic science's role in the courts, however, suggests that a much broader problem is the ease with which prosecutors have brought unproven forensic theories or unchallenged forensic experts into the courtroom.
In doing so, they harness the special sway such experts hold in court. Not even police officers are allowed the kind of latitude granted them--the freedom to give their opinion, not simply what they observed or heard.
Forensic experts and their testimony are being questioned because of two distinct forces reconfiguring the legal landscape.
In addition to the advent of DNA testing, U.S. Supreme Court rulings have sought to impose greater scientific rigor on forensic testimony.
In a defining 1993 decision, Daubert vs. Merrell Dow Pharmaceuticals, the court demanded that such testimony not simply meet the existing standard of "general acceptance" in its field, but also address some of the hallmarks of scientific inquiry--testing, peer review and rates of error.
That is precisely what has been lacking in many forensic fields, some of which have scrambled to catch up since the ruling while others continue to resist.
One facet of the problem is that while those involved in forensic disciplines wear the white coat of science and portray themselves as scientists, they often do not operate under the same rules as those in other scientific pursuits.
Crime labs regulate themselves, often operating without the scientific touchstones of experimentation and validation.
Consequently, lab analysts have been allowed to testify about such evidence as ear prints and examinations of shoe insoles, though little or no research exists to support their claims that these methods can identify matches.
Some respected figures in forensic science say the failure to address such problems and impose tougher standards is unacceptable.
"The stakes are too high--life, liberty, destroying families," said Dr. Joseph Davis, the chief Miami-Dade County medical examiner for four decades before he retired in 1996. "A person who is truly innocent is permanently disfigured or destroyed."
Lip prints seal fate
The adversarial nature of America's courts is supposed to insulate them from bogus testimony. Both sides may offer their experts. The judge and jury determine what testimony is reliable. And a just verdict is reached.
The safety valve malfunctions when those qualified as experts make unsubstantiated assertions, defense attorneys don't properly challenge those individuals, and judges and juries believe them.
Each of those failures was on display in the case of Lavelle Davis' lips. Though the questions raised by the use of lip print evidence don't prove his innocence, they cast doubt on the fairness of his trial.
A week before Christmas 1993, Patrick "Pall Mall" Ferguson was killed outside an Elgin apartment complex--felled by a single shotgun blast at close range.
Davis' first trial ended in a mistrial after a key eyewitness said she was backing off testimony she gave at the earlier trial of a co-defendant. At Davis' second trial, the woman said she was finally coming forward with the truth--that she saw him shoot Ferguson.
Even prosecutor Alice Tracy called the woman "an admitted liar" during the February 1997 trial.
Faced with that credibility problem, prosecutors pointed to physical evidence to corroborate their theory. They believed investigators had found it in the grass not far from the scene of the slaying: a roll of duct tape.
Tracy theorized how Davis' lip print could have been left on the sticky side of the tape. "He might have taken the duct tape to show one of the others what they were going to do with it if Patrick Ferguson ... started to scream," she told the jurors.
McKasson, who worked at the state crime lab in Carbondale, said he had examined lip prints in two other cases, though he had been unable to match a suspect to those prints.
He had no such reservations in the case of Davis, declaring the defendant's lips matched those found on the duct tape.
McKasson explained his conclusion by telling the court that lip prints were no different from any other form of what is called "impression" evidence.
"It's just a matter of the side-by-side comparison of impressions," he told the judge, who qualified him as an expert. "And to that degree it wouldn't matter whether it was a fingerprint, an ear print or a lip print."
Trying to buttress the credibility of a method rarely seen in American courts, a print examiner from the state police crime lab in Rockford, Leanne Gray, told the court that the FBI believes lip prints are a positive form of identification.
She was mistaken. The FBI "to this day hasn't validated lip print comparisons," said Ann Todd, spokeswoman for the bureau's lab in Quantico, Va.
Gray and the Illinois State Police declined to comment on the Davis case because his post-conviction petition seeking a new trial is pending.
For some jurors in Davis' trial, including Doris Gonzalez, the lip print evidence was convincing--much more than the eyewitnesses and others called by both sides who she said "were not very truthful people."
That made the lip print evidence crucial. "I mean, it was a big breakthrough for determining his guilt," Gonzalez said.
Davis' attorney, Lee Bastianoni, repeatedly challenged the methodology and qualifications of the two examiners during cross-examination but did not hire an expert to counter them.
Bastianoni instead tried to do the research himself. "I basically went to the library and read all the books I could on fingerprints and the scientific method," he recalled.
The novelty of the lip print evidence apparently did not trouble the Illinois Appellate Court, which affirmed Davis' conviction in a May 1999 ruling that illustrates how legal safeguards can fail to weed out questionable theories.
The court turned aside the challenge to the evidence, noting that the state experts had testified the FBI considered lip prints a "means of positive identification," and they "did not know of any dissent inside the forensic science community" challenging that assertion.
Had Bastianoni called the likes of Andre Moenssens, one of the deans of forensic science in the U.S., he would have discovered that many of Gray and McKasson's claims were unfounded.
A law professor emeritus at the University of Missouri-Kansas City and author of "Scientific Evidence in Civil and Criminal Cases," Moenssens happened to read the Illinois Appellate Court's decision.
He was so appalled that he wrote to the appellate defender's office, and at the request of Davis' appellate attorney, Kim Campbell, Moenssens agreed to file an affidavit for the post-conviction petition.
"You can't rely on your own cross-examination of the state's witnesses," said Campbell, now an assistant state's attorney in Downstate McLean County. "You have to have your own expert to say why this kind of science is unreliable. And there was nobody saying that at his trial."
In his affidavit, Moenssens wrote that "making the quantum leap ... to the ultimate notion of identifying an individual by the visible imprint of his or her lips, is a journey fueled by two elements: pure speculation and unadulterated conjecture."
The president of the American Academy of Forensic Sciences, the nation's chief professional society for forensic disciplines, was equally blunt in an interview.
"At this stage of the game, you can put ear prints and lip prints and nose prints and elbow prints all in the same category--unverified and unvalidated," said Ronald Singer, who also is director of the Tarrant County medical examiner's crime lab in Ft. Worth.
Since Davis' conviction, McKasson has retired from the state crime lab and runs his own document examination business. He gives frequent workshops around the country on how to be an effective expert witness and has co-written a book on the subject.
When told of the doubts raised by the FBI and others, McKasson repeated his defense of his work.
"It bothers me that the rest of them are wimping out," he said. "They're just worried about being attacked."
Pointing to the lip prints' apparent similarities on a computer screen at his home near Carbondale, McKasson added: "I still don't see what other choice I had, because there it was--it looked good to me. These two impressions came from the same person. There's no doubt in my mind."
Last week, a Kane County judge granted Davis a Jan. 31 hearing to make the case for a new trial, based in part on the questions about the lip-print evidence.
For Moenssens, the only thing as disturbing as McKasson's testimony was the Appellate Court's affirmation of it. "It doesn't say much for the courts' willingness to take the gatekeeper role seriously when it comes to novel techniques," he said.
FBI's fingerprint fiasco
Though lip prints may never be widely used or accepted, fingerprints have both a long history and the stamp of approval in courts and in the public consciousness. Yet a century of their use in solving crimes obscures a sobering reality: Despite claims that the discipline is an infallible science, it is neither infallible nor a science.
No standards exist for what portion of a fingerprint must be recovered before it is suitable for comparison. At most crime scenes, the police usually find only a fraction of a fingerprint, and that latent print, as it is called, frequently is smudged or otherwise distorted, making it difficult to compare.
Just as troubling, no research exists to say if people share fingerprint patterns--whether a few points of similarity or many.
Theoretical problems are just one issue. In 1995, one of the only independent proficiency tests of fingerprint examiners in U.S. crime labs found that nearly a quarter reported false positives, meaning they declared prints identical even though they were not--the sort of mistakes that can lead to wrongful convictions or arrests.
A recent episode in the war on terrorism underscored these shortcomings.
On May 6, federal prosecutors strode into a courthouse in Portland, Ore., and claimed the FBI had made a "100 percent positive identification" linking a local lawyer to a fingerprint found on a bag connected to terrorist bombings in Madrid.
Within weeks, the same prosecutors were forced to return to the courtroom and admit an international humiliation: The fingerprint analysis that led to the arrest of Brandon Mayfield was wrong.
But the FBI didn't realize it until Spanish authorities linked the fingerprint to an Algerian man, Ouhnane Daoud.
Not just one but three FBI analysts, all seasoned veterans, had made the same mistake. A fourth expert independently appointed by the judge erred as well when he determined Mayfield's prints were a match.
The Madrid fingerprint fiasco was one of the highest-profile embarrassments in the century since fingerprinting became one of the most trusted forensic tools, employed by police to catch everyone from burglars and car thieves to rapists and murderers.
In most cases, prints recovered at a crime scene are run through the FBI's massive databank of prints taken from arrests around the country. After the databank spits out a pool of potential matches, fingerprint examiners compare each of those with the crime-scene print.
They look for points of similarity among the circular ridges and lines that make up a fingerprint. Once a match is made, a colleague double-checks the work.
The FBI has long claimed that fingerprint identification is infallible. A top FBI fingerprint official has testified to a "zero error rate."
But even top officials with the leading fingerprint examiners' organization acknowledge that more research is needed to bolster the scientific foundation of fingerprinting.
"The debate is not so much do fingerprints work, but what is the science?" said Joseph Polski, chief operations officer of the International Association for Identification.
Another concern: Standards for determining how many points of comparison are needed to determine a match vary among police departments across the country. The FBI has no minimum; it says it relies on its analysts' experience and judgment to determine if fingerprints match.
Those issues are at the heart of the Mayfield case. The FBI said it found 15 points where the prints matched. Kenneth Moses, the former San Francisco crime scene examiner the judge consulted, testified he found 16 points. The Spanish police found eight and said that wasn't enough to declare a match.
Initially, the FBI found the print--lifted from a plastic bag containing detonator caps near the March 11 train bombings--of sufficient quality to compare and link Mayfield to the attacks.
After its error was made public, though, the government contended the image of the fingerprint it examined was of "no value for identification purposes."
"That's particularly difficult to understand since the Spanish police used it to identify Daoud, and the FBI had used it to identify Mr. Mayfield," said Steven Wax, the federal public defender in Portland who defended Mayfield.
One of the three FBI examiners responsible for the Mayfield match acknowledged the blunder. "We just did our job and made a mistake," John Massey said in an interview at his Virginia home. "That's how I like to think of it--an honest mistake."
Massey said he knew another examiner had already declared a match in the Mayfield case, but he said there was no pressure on him to concur.
While the Department of Justice's inspector general is reviewing the case, Massey said his faith in fingerprint comparisons is unshaken.
"I'll preach fingerprints till I die. They're infallible," Massey said. "I still consider myself one of the best in the world."
Such confidence in the face of error has many historical precedents in technical fields; physicians initially preferred to rely on their instincts, balking at using instruments as simple as a blood-pressure gauge that could be understood by laypeople.
Doctors didn't yield to the adoption of such instruments until insurance companies demanded quantitative measurements of patients' health, said Theodore Porter, a professor of the history of science at UCLA.
The public's "trust in the competence of practitioners and the implicit consensus within the field breaks down when skeptical outsiders challenge it," Porter said.
Fingerprint examiners have exhibited a similar resistance, saying their personal experience is proof enough of their reliability. The lingering question: Will the Mayfield case force them to embrace scientific validation?
Though it captured the most attention, Mayfield's brief arrest was only the latest in a string of cases in which fingerprinting was called into question.
The hunt to find who stabbed Alvin Davis to death seemed simple at first. After all, investigators in the working-class Philadelphia suburb of Upper Darby had found bloody fingerprints on a window fan leaning against Davis' decomposing body in autumn 1997.
After two days of examination, examiner Anthony Paparo said he had found at least 11 points of similarity between the bloody prints on the fan and those of a friend of Davis, Riky Jackson. To be certain, Paparo asked Upper Darby Police Supt. Vincent Ficchi, also a fingerprint examiner, to double-check his work. Ficchi concurred.
Defense attorneys rarely challenge fingerprint evidence. But Jackson's lawyer, Michael Malloy, dug deeper when he realized the case rested on the fingerprints. There was no confession from Jackson, no eyewitness.
A hairstylist who lived in Philadelphia, Jackson said police had shown him the fingerprints and told him they would convict him--maybe even put him on Death Row.
"They said, `See the fingerprints here? They're yours,'" Jackson said in an interview. "I told them, `There's no way they could be my fingerprints.'"
At trial, Paparo and two other experts testified how they had matched the bloody fingerprints on the fan to Jackson. Malloy got his own experts, two retired FBI agents, who testified the prints did not match.
A jury convicted Jackson, and he was sentenced to life. After his conviction, though, Malloy's experts filed a complaint with the International Association for Identification about Paparo and the two other experts who testified for prosecutors.
The complaint triggered a review of the evidence by the FBI, which concluded that Paparo had erred.
Two days before Christmas 1999, Jackson walked out of a Pennsylvania jail. Authorities have yet to link the prints to anyone else.
To this day, Paparo denies misreading the prints. "I'm not going to lock someone up just to clear a case," he said, standing in front of the illuminated screen at the police department where he made the comparison.
The most significant challenge to fingerprinting came in 2002 in another Pennsylvania case, a drug conspiracy with charges of multiple murders. Presiding over it was Judge Louis H. Pollak, a former dean of Yale Law School respected by lawyers on both sides of the aisle in Philadelphia.
In January 2002, Pollak issued a stunning decision: that there was insufficient scientific basis for examiners to declare fingerprint matches.
It was the first time a U.S. trial judge had rejected fingerprint comparison evidence. Despite its long history of acceptance, Pollak ruled, fingerprinting lacked the testing, peer review, uniform standards and known error rates called for under the Supreme Court's new Daubert standard.
Prosecutors asked Pollak to reconsider his ruling, and for three days in February of that year he held hearings that put fingerprinting to the test.
An FBI agent testified that examiners scored well on the bureau's own proficiency tests. But a London fingerprint consultant who had worked for years for Scotland Yard testified for the defense that the tests were too easy. The prints were too clean, he said, unlike what fingerprint examiners have to deal with at crime scenes.
The British expert, Allan Bayle, said his officers, if given the same kind of proficiency tests, would "fall about laughing."
After hearing both sides, Pollak acknowledged the problems with the FBI's proficiency testing. But the judge said he was convinced that examiners in Britain and the U.S. generally agreed on the methods for analyzing prints and that the testimony of an FBI fingerprint expert gave him "a substantially more rounded picture of the procedure."
In the end, the judge who had called into question one of the bedrock forensic sciences gave it a reprieve, agreeing that the FBI had never made a mistake.
"I have found, on the record before me, that there is no evidence that certified FBI fingerprint examiners present erroneous identification testimony," Pollak wrote, before concluding, "In short, I have changed my mind."
His ruling seemed to put the issue to rest. Then, two years later, the FBI wrongly accused Mayfield in the Madrid case.
Fighting unproven science
In the criminal justice system, juries often decide a person's guilt. But judges have broad discretion over what those jurors hear, including which forensic experts and what kind of forensic evidence.
For decades, most judges screened scientific testimony according to a 1923 federal decision. Frye vs. United States said such testimony must be based on principles "sufficiently established to have gained general acceptance in the particular field in which it belongs."
In 1993, the U.S. Supreme Court created the stricter Daubert standard, which held that trial judges also "must ensure that any and all scientific testimony or evidence admitted is not only relevant, but reliable."
But the Daubert standard applies only to federal courts and the state court systems that choose to adopt it. Some state courts, including Illinois, continue to use the Frye guidelines.
Even though judges rarely bar forensic experts from testifying, the director of the Justice Department's research arm argues that the bench is aggressive in its gatekeeper role.
"I have a lot more faith in judges," said Sarah Hart, director of the National Institute of Justice. "They can even hire their own experts to inform them. In this advocacy system ... you can get a lot of information on this stuff."
But some jurists themselves say judges are ill-prepared for this part of their job.
Haskell Pitluck, a retired McHenry County judge and former president of the American Academy of Forensic Sciences, described the problem facing many in the justice system.
"If lawyers could do science, they'd be doctors," he said, noting that he is better versed in forensics than many jurists, "and I don't feel qualified to make many of these calls."
A national survey of 400 state trial judges published in 2001 found that while nearly all jurists believed their gatekeeping role was appropriate, only 4 percent had a clear understanding of the key scientific concepts of probability and error rates.
Some forensic disciplines certify experts in their fields, but that's no guarantee of quality.
"Too often, the lawyers don't do their homework enough so they can properly cross-examine these people," Pitluck said. "They come in and say, `I'm an expert.' And some lawyers simply roll over."
Every new forensic discipline has been met with skepticism. Even DNA was not readily embraced when first used in the 1980s to identify suspects, because it was largely untested in the courtroom.
This underscores a central dilemma of the justice system: how to distinguish promising forensic methods and their practitioners from junk science and their charlatans.
One of the more bizarre crime-lab tools has been championed for more than 15 years by a Dutch police officer, Cor van der Lugt. He contended that when pressed upon a flat surface, a person's ear leaves distinct marks that can later be matched through its unique shape, size and contours.
Van der Lugt testified in the 1997 murder trial of David Wayne Kunze in Vancouver, Wash., that he had examined ear prints in over 600 cases abroad.
The Dutch officer, according to court documents, said he thought it was "probable" that Kunze had left his ear print when he pressed against a bedroom door to listen before entering to kill the man sleeping inside. When asked on the stand how certain he was, he said: "I'm 100 percent confident of that opinion."
Michael Grubb, then the manager of the Washington State Patrol Crime Laboratory in Seattle, stopped short of declaring an exact match but testified at the trial that Kunze was "a likely source."
Grubb, now director of the San Diego crime lab, said the Kunze case is the only ear print case he had worked on.
"I examined ear prints from 130 other individuals as part of the Kunze case," Grubb told the Tribune, and "none of the other 130 ear prints were similar."
Kunze was convicted and sentenced to life in prison.
In this instance, though, the courts' checks-and-balances system worked. Kunze's conviction was overturned after an appellate court ruled that the ear print evidence was not reliable enough for such declarations of certainty. Prosecutors later dropped the charges.
Distinguishing the forensic fringe from the cutting edge can be difficult enough; keeping a debunked science from re-entering the courts can be even tougher.
North Carolina anthropologist Louise Robbins helped send more than a dozen defendants across the country to prison or to Death Row with her self-proclaimed power to identify criminals through shoe prints. On occasion she even said she could use the method to determine a person's height, sex and race.
By the time Robbins died in 1987, appeals courts had overturned many of the cases in which she had testified. And the American Academy of Forensic Sciences, in a rare rebuke of one of its members, concluded her courtroom work was not grounded in science.
But in a laboratory at the headquarters of the Royal Canadian Mounted Police in Ottawa, the effort to determine identity from feet and shoes is getting new life.
Sgt. Robert Kennedy, a veteran fingerprint analyst, says he can tell who wore a shoe by comparing impressions left on an insole with a person's foot.
Kennedy calls it "barefoot morphology." Like Robbins, his work has helped prosecutors obtain convictions.
"I know there've been questions about this. Louise Robbins was a real problem," Kennedy said in an interview in his office. But "you don't want to just let an area of forensic science go by the wayside. It's good evidence."
Unlike Robbins, Kennedy has tried to base his work in science. Since the early 1990s, he has been visiting army bases and other sites to build a database of footprints that now exceeds 10,000 sets.
In the 1998 trial of Jeffrey Jones in South Carolina, Kennedy's work proved crucial to sending Jones to Death Row.
Police investigating a double murder believed a boot that had left a bloody impression in the victims' kitchen belonged to the killer. They matched the impression to a boot found in a house that Jones shared with another man, James Brown, who admitted his role in the killings. In exchange for a life sentence, Brown testified against Jones.
No physical evidence linked Jones to the crime, and he denied involvement. Though the boots were size 9 1/2 and Jones wore between an 11 and 11 1/2, prosecutors said he was wearing them when the murders were committed.
At the trial, South Carolina crime lab analyst Steven Derrick, who had never before testified to such a comparison, said he examined the boot insole and an impression from one of Jones' feet.
Derrick concluded that the only way someone else's foot could have made the impression on the boot insole would be if the person had precisely the same foot characteristics--such as the shape and the distance between toes.
Derrick also testified that he had not made a comparison with the feet of Brown, who claimed the size 9 1/2 boots were too big for him.
Kennedy vouched for Derrick's work as well as the field of barefoot morphology, testifying that he talked Derrick through the comparison process.
In 2001, the South Carolina Supreme Court reined in such evidence, ruling there was insufficient science to support it. The court ordered the state to either try Jones again or set him free.
Even with the ruling, prosecutor Dayton Riddle said he would use the insole evidence again when he takes Jones back to trial.
"That's good science, despite the fact it got reversed," Riddle said. "I think what happened there is that I was a little bit ahead of the curve."
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Forensic science: From bullets to brain fingerprinting
The analysis of alcohol, drugs and poisons in the body, as well as testing of seized evidence for the presence of narcotics such as cocaine and heroin.
1836: Scottish chemist James Marsh develops a test to detect arsenic after a jury in a murder trial had rejected his testimony about the presence of the poison in the victim.
Matching fingerprints through the individual characteristics said to make each person's unique.
1892: The modern system of fingerprint identification begins to take shape with Sir Francis Galton, a British anthropologist and cousin of Charles Darwin who asserts the uniqueness of fingerprints.
The process of matching bullets found at crime scenes with bullets fired from a suspect's weapon.
1912: Victor Balthazard, a professor of forensic medicine, asserts that machine tools used to make gun barrels never leave exactly the same markings. After studying images of gun barrels and bullets, Balthazard reasons that every gun barrel leaves a signature set of etched grooves on each bullet fired through it.
Hair and fibers are examined to connect a suspect to a crime scene or a victim.
1920: Edmond Locard, professor of forensic medicine at France's University of Lyon, publishes a criminal science volume that espouses the principle that "every contact leaves a trace."
The examination of fire damage to determine a fire's cause, origin and whether it was intentionally ignited.
1962: John A. Kennedy writes the textbook "Fire and Arson Investigation," which puts forth some theories that have since been debunked.
The examination of dental records to determine a person's identity, such as in mass fatalities. Its more controversial application, bite-mark comparisons, links suspects to bite wounds on crime victims.
1968: Dr. Warren Harvey, an odontologist, is the first to identify a suspect's bite marks, which led to the conviction of a murder suspect in Scotland.
The comparison of an individual's genetic profile with the genetic profile from evidence found at a crime scene.
1993: Kary Mullis wins a Nobel Prize for polymerase chain reaction, a process that greatly reduces the time required and amount of evidence needed to do DNA testing.
Using a headband with sensors, the technique measures brain waves. In theory, sensors detect when the guilty recognize details of a crime. It's unclear if it is the next great forensic tool or another chapter of junk science.
2001: After Dr. Lawrence Farwell, a neuroscientist, develops brain fingerprinting, it is first presented in court to an Iowa judge, who disregards it.
Sources: Forensic DNA Consulting, Bruce Anderson's 1998 University of Arizona doctorate dissertation, National Library of Medicine, McGraw-Hill Encyclopedia of Science & Technology, Science Fair Projects Encyclopedia, Crime Library
Gentry Sleets, Chris Soprych and Phil Geib/Chicago Tribune
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The project team
Flynn McRoberts, Steve Mills and Maurice Possley are veteran projects reporters for the Tribune and have contributed to ground-breaking investigations of criminal justice in America over the last six years. Their work has included stories about flaws in the death penalty, false confessions and immigration policies targeting Muslims. Alex Garcia has photographed Illinois' historic clemency hearings; his photos also were featured in the series "The Legacy of Wrongful Convictions."