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The Fallibility of Forensic Science: Crime-Solving Tool Can Lead to Wrongful Convictions—and Belated Exonerations

by Rick Anderson

It’s the ultimate crime-solving tool, enabling prosecutors to bring seemingly rock-solid charges against accused murderers and rapists while also using it to re-open and solve dust-collecting cold cases. Victims and their families consider it a godsend and television watchers marvel at its consistency in bringing happy endings to crime dramas.

We’re talking about forensic science, of course, an investigative discipline loaded with fascinating and persuasive methods of gathering evidence to present in the courtroom. Included are advanced versions of fingerprint matching (images can now be tested to determine when the print was left), DNA analysis (today being used successfully on older, ever-smaller specimens) and exotic experiments, such as testing a rape victim’s hair bacteria for traceable micro-organisms shed by the attacker.

Results are presented daily to juries across the country to help them decide who is guilty and who is not, or in some cases, who will live and who will die.

What they’re unlikely to hear, however, is that frequent miracles of forensic science are usually the only way to reverse the serious mistakes of forensic science. They are frequent, too, researchers say.

Misapplied Science

The “misapplication” of forensic science is the second most common contributing factor to wrongful convictions, according to a study by the Innocence Project, which has helped free 362 unjustly imprisoned men and women since 1989. The study found that faulty crime science was behind almost half — 45 percent — of the convictions that relied on the police and prosecutor’s DNA evidence.

Cathy Woods, now of Gig Harbor, Washington, sees some wicked irony in those statistics. DNA testing wasn’t much of an investigative tool back in 1980 when she was convicted of murder in Reno. A 23-year-old bartender at the time, Woods was accused of slitting the throat of 19-year-old University of Nevada nursing student Michelle Mitchell after she supposedly rebuffed Woods’ sexual overtures. Police asserted Woods was lesbian and that she later confessed — while they grilled her at a mental hospital.

She was sentenced to life without parole, but ended up serving 35 years in prisons and locked in mental wards before she was released in 2016. She had aged poorly, enduring electroshock therapy and losing a number of teeth along with decades of freedom. She still suffered from the schizophrenia that plagued her since she was 12. But she had achieved a status no one else had (or wants): Woods had become America’s longest-serving wrongly convicted female inmate, according to the National Registry of Exonerations. She had killed no one.

DNA testing wasn’t around to possibly prevent her conviction four decades earlier. But it was there to, by chance, reverse it. Woods was exonerated by a routine DNA test given to another prisoner thousands of miles away. Rodney Halbower, 69, a suspected serial killer and convicted rapist, had spent decades in prison. In 2016, he was being moved to another facility from an Oregon lockup and was given a required DNA test in the process. He had been given DNA tests in the past, without consequence. But this time, bingo. Government computers matched his DNA with samples taken from the Reno crime scene that were later loaded into a federal database. Cathy Woods was free to go.

Now 67, Woods lives near her caregiver and is pursuing a lawsuit against Reno and Nevada officials, claiming she was railroaded into prison and then forgotten. Nevada has offered an apology but is one of 24 states that doesn’t automatically compensate the wrongfully convicted. Woods’ attorney, Elizabeth Wang, says her client is thankful for the DNA test that unexpectedly revealed the real killer, but – the evidence sat there more than 35 years? How did that happen?

“Prison is difficult enough to handle on its own,” Wang told me. “What must it be like to also be mentally ill — and innocent?” And not know there had always been forensics evidence to free her. “The police didn’t care if she was guilty or not,” Wang says. “They just wanted to close a case.”

Flawed cases

While many of the exoneration cases have generated at least modest news coverage, the fickleness of forensics hasn’t gotten the headlines it deserves. Its serious quirks are becoming better known today, but the world seemed not to have noticed or cared when the science collided with itself in two high-profile murder trials about a decade ago.

On separate continents, forensics helped to convict Amanda Knox of murder in Italy and helped to exonerate O.J. Simpson of double murder in Los Angeles.

Then it turned around and helped set Knox free and prove Simpson was responsible after all.

As their criminal, civil, and appeal hearings demonstrated during two decades of courtroom battles, the reliability of forensic science depends on the credibility of the scientist – the medical examiners, lab technicians, experts, and others who gather and interpret evidence. Many of them also take the stand to explain a complicated science that has evolved into popular home DNA testing kits for those interested in filling out their family trees or seeking DNA-based recommendations on diet and fitness.

DNA matching turned out to be both a blessing and a curse as the Knox and Simpson cases progressed to trials and appeals. Ultimately, in 2015, Knox and her former boyfriend Raffaele Sollecito were exonerated in the 2007 murder of Meridith Kercher due to faulty forensic evidence and what a judge called “stunning flaws” in the investigation.

In the Simpson case, a 1997 civil jury, hearing much the same evidence as the criminal jury did in 1995 but without the circus atmosphere, awarded $33.5 million in damages to the families of Simpson’s alleged victims — ex-wife Nicole Brown and her friend Ron Goldman. Simpson wasn’t found “guilty” but he was found “liable.” He could still say he was not a convicted killer, but Goldman’s father, Fred Goldman, said the civil finding was the equalizer. “The jury decision of last Tuesday was the only decision important to us, to find the killer of my son and Nicole responsible,” he told reporters. “The money is not an issue. It never has been. It’s holding the man who killed my son and Nicole responsible.’’

The two cases left a residue of doubt about forensic science that has grown into deep concern today, judicial activists say. Just how competent, consistent, and ethical are the medical examiners, lab techs, and crime-scene personnel entrusted with the crucial task of documenting the accused’s guilt or innocence? And why do they never have these problems on CSI?

Barry Scheck, who co-founded the Innocence Project in 1992, believes forensics is a valuable science that also has fatal flaws. Actually, he said, that was the point he was trying to make after becoming a surprise member of the Simpson defense team. “It was a watershed case, but not in ways that people suspect,” Scheck told reporters after the stunning not guilty verdict (by a jury that was sequestered and could likely commiserate with the jailed Simpson after 134 days of confinement).

“We did not challenge the underlying reliability of DNA testing methods; we attacked the way that evidence was gathered and processed. We had a 21st century technology and 19th century evidence collection methods.”

In addition to forensics mistakes, say Scheck’s organization, the major causes of wrongful convictions include faulty witness identification of suspects, perjury by those reporting crimes or testifying on the witness stand, false pleas and confessions, and police and prosecutorial misconduct. To the convicted victims of those failures, justice is hardly living up to its name.

U.S. exonerations now average three a week, according to The Innocence Project and the National Registry of Exonerations. The registry lists 2,292 exonerated prisoners since 1989 whose sentences total more than 20,265 years of freedom lost. The cost was higher for some. Since 1973, 144 death row prisoners have been exonerated. That’s less than 2 percent of inmates sentenced to die. But it’s also only about half the number of condemned prisoners thought to be wrongly convicted, according to several studies.

Some researchers believe more than a few death-rowers have wrongly been put to death. A greater effort is needed to determine exactly how many have died, they say. A so-far incomplete U.S. government-backed study group reported in 2015 that 32 men convicted through possibly faulty forensics evidence were sentenced to death. Researchers say at least 14 of them either died in prison or had already been executed.

Overall, the number of prisoners wrongly locked up is also a guessing game. A registry study concedes that 2,000-plus exonerations over almost three decades “is a tiny number in a country with 2.3 million people in prisons and jails,” but adds that “These cases merely point to a much larger number of tragedies that we do not know about.”

Moved By Unjustness

We may be learning, and even caring, more. Americans, who typically have little empathy for the country’s incarcerated, seem moved by unjust convictions, perhaps realizing that can happen to anyone. As reporters and TV producers have come to learn, readers and viewers react sympathetically to stories of the imprisoned who are factually innocent.

In a memorable Law & Order episode that can still be viewed in re-run, for example, detectives investigating the murder of an ex-con stumbled upon the wrongful conviction of a suspect in a related killing 10 years earlier. In a sly plot twist, the detectives learned that their boss, Sergeant Anita Van Buren (S. Epatha Merkerson), had been the lead investigator in the faulty case. They later discovered that, without Van Buren’s knowledge, a lab tech had intentionally linked non-matching fingerprints from the crime scene to the suspect, and had done so in other instances to help police and prosecutors build their cases. If a person was charged, he or she must be guilty, the helpful tech explained.

That fictionalized account, challenging the common trust in forensic practitioners, mirrored real instances of science failures — some of which were intentional. As recently reported, “Of course, [forensic] evidence is available for experts with trained eyes and the proper equipment, but the science isn’t without fault. Even those at the upper echelons of criminal justice have been found guilty of fraud in forensics. In 2015, the FBI admitted to decades of relying on faulty hair analysis in trials, a grave error in criminal proceedings.”

Even a September 2016 report from the President’s Council of Advisors on Science and Technology cast aspersions on some forensics methods because of their insufficient testing procedures. The council found that “only single-source DNA had both of the requisite types of scientific validity: foundational (i.e., accurate in a controlled lab environment) and applied (i.e., applicable in a real world context). While multiple-source DNA, fingerprinting, and other forensic methods may be useful, they require further testing to establish both foundational and applied validity.”

Still, that’s evidence that can be openly debated in court, where jurors, assuming they’re not swayed by the forensic miracles on TV, can judge for themselves. More dangerous, as in the Law & Order episode, is the rogue examiner or lab tech whose tampering may not surface until years later, if at all. compiled some examples of this, calling its 2016 report “10 Heinous Cases of Misconduct by Crime Investigators.”

They include Fred Zain, a police chemist in West Virginia and chief of physical evidence in Bexar County, Texas, who spent much of his forensics career habitually faking lab results and lying under oath to help prosecutors obtain convictions. For 13 years, Listverse reported, “prosecutors in two states sought out Zain’s ostensibly expert opinions, never questioning the fact that he managed to produce evidence with a certainty that other lab technicians couldn’t approach. This faith in Zain’s abilities sent untold numbers of innocent men behind bars, primarily for rape and murder charges. While some of those men were exonerated, the exact number of cases influenced by Zain is unknowable. And, from what is known, it’s clear that Zain’s dissembling reach was tremendous.”

In West Virginia alone, Zain may have lied during as many as 182 different investigations.

In addition to his work in a Texas crime lab, Zain served as a forensics consultant to 20 other states, raising the possibility that he lied at thousands of primarily rape and murder trials. It was costly for defendants and taxpayers. West Virginia alone paid $6.5 million to compensate innocent defendants convicted by Zain’s deception. “For Zain’s many victims,” Listverse observed, “exoneration and compensation are the only justice possible.

Fred Zain died of cancer after the first attempt at holding him accountable for his misdeeds ended in mistrial, and before retrial could begin. One can only hope that, in time, his legacy will evolve into one of wrongs righted by a wiser justice system, rather than the virulent injustices he authored.”

In Douglas County, Nebraska, sheriff’s crime-scene investigator David Kofoed went to prison after he was caught manipulating DNA evidence in a series of murder cases. In one, Kofoed planted traces of blood that tied two suspects to a 2008 murder scene and led to their convictions. One of the suspects, a mentally disabled man, was also forced by other officers to giving a false confession. Fortunately, additional evidence later led to the actual killers and exposed Kofoed’s deception. He served two years and was successfully sued by the two wrongly accused suspects for $6.5 million, Listverse writer A.C. Grimes reported. In other cases, Kofoed was suspected of planting blood and submitting fake-DNA evidence.

On other fronts, news outlets have been reporting medical examiner and crime-lab failures for decades. Writer Matt Clarke, in a 2011 report for Prison Legal News, focused on the almost legendary forensic breakdowns plaguing the Texas medical examiner system.

Examiners, he wrote, “have a certain mystic quality and are perceived as both doctors and sleuths who use scientifically-proven forensics techniques to reconstruct crimes, determine causes of death and identify the guilty. The reality, though, is almost exactly the opposite.
“In fact, critics of Texas medical examiners say they are ‘the last bastion of junk science.’ Such criticisms are bolstered due to a lack of accreditation and performance standards, a shortage of qualified personnel, excessive workloads, lax oversight and a profit motive among some medical examiners which, taken together, have brought their reliability and competence into question.”

With little to no training, Texas MEs were given near-free reign to investigate deaths with little to no oversight. “Until fairly recently the Texas Medical Board did not discipline medical examiners because it did not consider the performance of an autopsy to be the practice of medicine, as there was no potential to harm a patient,” Clarke reported.

Besides, officials said, no one’s complaining. To that, Tommy Turner, a former special prosecutor who won a conviction against a Lubbock County medical examiner for falsifying autopsies, stated, “First of all, the person that you’re performing work on is dead. They’re not going to complain.” But there are people who have a legitimate right to complain about unqualified personnel performing autopsies without adequate oversight—the individuals erroneously implicated in crimes.

‘Slipshod’ work

Turner called the work of some medical examiners “slipshod.” Take, for example, the case of a 23-year-old male sex offender who faked his own death using the body of an 81-year-old woman who had died a year earlier. He dug up the body and burned it in his car, leaving his identification nearby. The Travis County medical examiner’s office identified the body as that of the man and even noted a penis and urine in the bladder on the autopsy report, both of which were impossible. The response by Dr. Vladimir Parungao, who conducted the autopsy? “I should have been more careful,” he said. “I let my guard down.” He appears to have confused care with competence.
Across the U.S., forensic failures, accidental or intentional, result in the costly reversals of wrongful and legit convictions, along with the denial of justice to victims and their families. Crime lab mistakes have in some instances been astronomical — one Massachusetts forensics technician may have set some sort of record for falsifying drug tests a few years back. But some of the greatest screw-ups were notched by the country’s arguably most-respected and efficient law enforcement agency, the FBI.

As The Washington Post reported in 2015, of 28 examiners with the FBI Laboratory’s microscopic hair comparison unit, 26 of them “overstated” forensic matches in ways that favored prosecutors in more than 95 percent of 268 trials reviewed. The findings of the ongoing review were released by the National Association of Criminal Defense Lawyers and the Innocence Project, which assisted in what was called the country’s largest post-conviction review of questioned forensic evidence.

The review, which turned up those 34 cases of apparently wrongfully convicted death row prisoners we mentioned earlier (14 of whom died in prison or were executed), highlighted the failure of the nation’s courts to keep bogus scientific information from juries, legal analysts said. “The question now,” the Post reported, is whether “authorities and the courts will respond to findings that confirm long-suspected problems with subjective, pattern-based forensic techniques — like hair and bite-mark comparisons — that have contributed to wrongful convictions in more than one-quarter of 329 DNA-exoneration cases since 1989.”

Peter Neufeld, the other co-founder of the Innocence Project, saluted the FBI and Justice Department for their collaboration on the review, but said, “The FBI’s three-decade use of microscopic hair analysis to incriminate defendants was a complete disaster ... We need an exhaustive investigation that looks at how the FBI, state governments that relied on examiners trained by the FBI, and the courts allowed this to happen and why it wasn’t stopped much sooner.”

The Post’s story helped inspire Conor Friedersdorf to write a piece for The Atlantic called “CSI is a lie.” The Post story had included a link to its 2012 coverage of problems with FBI forensic analysis, he noted. But, Friedersdorf wrote, “the existence of shoddy forensics has been so clear for so long in so many different state and local jurisdictions that the following conclusion is difficult to avoid: Neither police agencies nor prosecutors are willing to call for the sorts of reforms that would prevent many innocents from being wrongfully convicted and imprisoned, and neither the Republican nor the Democratic Party will force their hands.”

In Texas, America’s death penalty capital, Friedersdorf wrote, “forensic analysts weighing in on cases of rape and murder literally tip the scales in favor of life or death for a defendant. It’s a grim burden that grows ever heavier in light of the fact that, for decades, the Houston Police Department crime lab has relied on faulty DNA analyses and bogus courtroom testimony that, according to a lab director, have tainted at least 5,000 to 10,000 cases.

“Forensic analyst James Bolding demonstrated overwhelming incompetence and willful dishonesty in his work, appearing not to grasp even the basics of blood sample analysis, while providing courtroom testimony that wrongfully imprisoned men like George Rodriguez, who languished behind bars for 17 years for a rape he didn’t commit, and Josiah Sutton, who was wrongly incarcerated for four years.

“Bolding, and the hundreds of cases he compromised, were emblematic of a culture of inadequacy at the Houston lab, where numerous technicians knowingly conducted unreliable analyses in a lab which itself was woefully sub-par. Disorganization was rife, and records were regularly falsified. Even before the shoddy evidence testing began, samples were often contaminated via a leaky roof.”

Scandals and fallout

In recent years, scandals have rocked some medical examiner offices and crime labs, with fallout continuing to this day. The New York City medical examiner’s office announced in 2013 it was reviewing more than 800 rape cases from a 10-year period. Officials suspected evidence in those cases may have been mishandled by a lab technician, Serrita Mitchell, who resigned when her work was questioned. A later report spread the blame around, noting her supervisors knew about her “myriad failures” but didn’t fire her. Officials said Mitchell often overlooked stains on the clothing of sexual assault victims, possibly missing a chance to find crucial DNA evidence. In one case, she found six stains on a T-shirt and pair of jeans, evidence from a sexual assault. One of her supervisors, however, found 20 other stains that weren’t tested for DNA.

Around the same time, a chemist who worked at a since-closed state drug lab in Boston was indicted for her alleged mishandling of tens of thousands of drug cases during her nine-year tenure. Annie Dookhan was accused of evidence tampering, perjury, and obstructing justice for faking test results, sabotaging drug samples, forgery, and falsely claiming to have a master’s degree.

Dookhan admitted to police she changed and faked test results to cover up her laziness – it was easier to make up results than undertake the tedious lab examinations. She thus was sometimes able to do 500 drug analyses a month, five times the normal average. “I messed up,” she told investigators. Dookhan was sentenced to up to seven years in prison but was paroled in 2016 after serving just three.

It’s clear that reforms are needed to ensure that the science is done scientifically and its practitioners stay honest. While many prosecutors opposed any drastic revamping that could make their work more difficult and perhaps affect some past convictions, defense attorneys and some judges are speaking out in favor of change. The Innocence Project has proposed a series of reforms that include ways to improve error identification and prevention, expand transparency of information, and ensure that outcomes are just (full list below).

Similar proposals were laid out in a 2016 report by the President’s Council of Advisors on Science and Technology. Candid and comprehensive, the 183-page document pulls no punches in describing the science’s shortcomings.

Forensics “is at a crossroads,” the report concludes. But it’s still waiting for someone to decide which way to turn.

Outline of Innocence Project proposed reforms:

Through the examination of more than 350 exonerations, the Innocence Project has seen the many ways forensic science can be misapplied. We use the term “misapplication of forensic science” to describe several kinds of problems, including:

Unreliable or invalid forensic discipline. Studies have demonstrated that some forensic methods used in criminal investigations cannot consistently produce accurate results. Bite-mark comparison in which an identification of a biter is made from a bite mark made on skin is an example of an analysis that is unreliable and inaccurate.

Insufficient validation of a method. Some of the forensic disciplines in use may be capable of consistently producing accurate results, but there has not been sufficient research to establish validity. Accuracy of a method should be established using large, well-designed studies. Without these studies, the results of an analysis cannot be interpreted. Analysis of shoeprints as a basis of identifying the unique source of a print is an example of a method that has not been sufficiently validated.

Misleading testimony.

-- Sometimes forensic testimony overstates or exaggerates the significance of similarities between evidence from a crime scene and evidence from an individual (a “suspect” or “person of interest”), or oversimplifies the data. Examples include testimony that suggests a collection of features is unique or overstates how rare or unusual it would be to see these features, implying that it is quite likely that the suspect is the source of the evidence, and testimony that doesn’t convey all possible conclusions, as can arise with masking in serology testing.

-- Sometimes forensic testimony understates, downplays, or omits the significance of an analysis that establishes that an individual should be excluded as a possible suspect. An example is testimony that an analysis is “inconclusive” when in fact, the analysis excluded the suspect.

-- Sometimes forensic testimony fails to include information on the limitations of the methods used in the analysis, such as the method’s error rates and situations in which the method has, and has not, been shown to be valid.

Mistakes. Like everyone, forensic practitioners can make mistakes, including mixing up samples or contaminating specimens. These can occur in any type of science or laboratory testing, even in well-developed and well-validated fields.

Misconduct. In some cases, forensic analysts have fabricated results, hidden exculpatory evidence, or reported results when testing had not been conducted.

The first major scientific institution to investigate this problem across the board was the National Academy of Sciences (“NAS”) in its report, “Strengthening Forensic Science in the United States: A Path Forward,” released in 2009. This report noted that “imprecise or exaggerated expert testimony has sometimes contributed to the admission of erroneous or misleading evidence.” It also found that some forensic techniques, particularly those that deal with comparing patterns or features (such as tire tread impressions, bite marks, fiber, or hair), have not been subjected to sufficient scientific evaluation and noted that the scientific basis for arson investigations should be strengthened.

The same concerns were reiterated and expanded upon in the 2016 report, “Forensic Science in Criminal Courts: Ensuring Scientific Validity of Feature-Comparison Methods,” by the President’s Council of Advisors on Science and Technology. This report examined the research underlying specific forensic feature comparison disciplines, evaluated their accuracy and reliability, and made recommendations to various federal agencies to strengthen these disciplines. Among the recommendations was the need for better resources to support judicial training given the changing landscape in the evaluation of forensic evidence and state of validation of various forensic techniques.

Reforms and Solutions

The serious problems identified in forensic science and its practice in the United States can only be addressed by a commitment to reform at multiple levels. The Innocence Project is working at the national level to support efforts to improve forensic science disciplines through research and standards setting, including:

• Ensuring that the National Institute of Standards and Technology (“NIST”), a preeminent, independent science agency with measurement expertise, conducts scientific evaluations of the validity of the forensic disciplines.

• Increasing funding for research at science-based agencies and institutions in accordance with a well-developed strategic plan to establish or strengthen the fundamental science underlying forensic science disciplines.

• Developing rigorous national standards, recommendations for documentation of forensic sciences, and guidelines for reports and testimony for those forensic disciplines that have been shown to be based on robust and reliable science.

• Supporting judicial training and other efforts to ensure that future decisions in admissibility consider the validity of a forensic test in general and the validity of the test as applied in the specific case at hand.

The National Commission on Forensic Science (“NCFS”) is advising the nation on this path forward and has provided recommendations to the attorney general and the director of NIST on several important topics, including a uniform code of professional responsibility, requirements for report contents, discontinuing the use of the phrase “reasonable degree of scientific certainty,” and the necessity of independent scientific evaluation of the validity of forensic science disciplines.

To improve the quality of forensic science practices in laboratories, the Innocence Project supports efforts to promote error identification and prevention, improve transparency of information, and ensure just outcomes, including:

• Adoption of procedures that reduce the influence of “cognitive biases” on an analyst, such as preventing access to extraneous and potentially biasing information.

• Adoption by every forensic science service provider of a root cause analysis procedure, as recommended by the NCFS, the results of which should be transparent and available to the public.

• Continuation of federal funding for the Coverdell Forensic Science Improvement Program to support state and local forensic science service providers and to ensure independent external investigations when allegations of negligence or misconduct are made.

• Retrospective review of cases when systemic misapplication of forensic science is identified. Examples include the joint microscopic hair comparison review undertaken by the Federal Bureau of Investigation, the National Association of Criminal Defense Attorneys, the Innocence Project, and reviews conducted by the Texas Forensic Science Commission in response to complaints filed in the state.

• Establishment of a duty-to-correct mistakes and a duty-to-notify affected defendants when errors or significant breaches of scientific principles or ethics are identified.

Lastly, as a matter of fairness and justice, the Innocence Project supports judicial examination (post-conviction review) in cases in which unsound science may have contributed to a conviction. Statutes addressing this issue have recently been passed by Texas and California. 

Sources:, President’s Council of Advisors on Science and Technology 2016 review of forensic practices,,, 2011 report on forensic failures,,, National Registry of Exonerations, National Association of Criminal Defense Lawyers

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