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Wrongful Convictions – The Impact of Mishandled Evidence on the Accused

April 27, 2022

Tracker’s most popular blog, for two-and-a-half years running, has been about wrongful convictions.  Specifically,  THE IMPACT OF MISHANDLED EVIDENCE ON THE ACCUSED. In the last month alone, 156 readers – who we assume to be in the field of evidence management – have turned to this article to discover how the accused may actually be the victims due to consequences of mishandling evidence or inaccurate forensics. 

Knowing this is a subject near and dear to the heart of the evidence management community, we thought it was high time we revisited this topic.   

We all know that mishandled, damaged, or lost physical and digital evidence can happen at any time during the chain of custody: at the crime scene, during the packaging, when transferring, while in storage, and even during analysis.

In the Tracker article mentioned above, we included excerpts from SACurrent that identified a negligent police officer. Let’s revisit the highlights from that article…  “Detective Kenneth L. Valdez was indefinitely suspended from the SVU for a number of violations that took place over two years, according to a suspension report obtained by the SACurrent. Valdez failed to submit forensic evidence to the Bexar County Crime Lab for any of the 27 cases he was assigned to investigate over that time period. 

Of the 27 cases, 17 contained evidence that specifically needed forensic testing. The report claims Valdez also failed to properly take care of evidence recovered in an investigation — inspectors found unmarked cell phones, DVDs, CDs, and cash in his office, along with several unmarked envelopes containing saliva swabs. 

At least twice, Valdez did not follow up on crucial information given to him by the crime lab about possible suspects in his cases. The report mentions one of his cases where he ‘failed to act’ after learning that a known suspect’s DNA was found on a victim. He instead concealed the information and closed the case without his supervisor’s approval.

‘There simply is no excuse for such improper behavior, and Detective Valdez is not representative of the thousands of men and women in our police department who are passionately committed to protecting the most vulnerable among us,’ said San Antonio City Manager Sheryl Sculley in a press release’.”

Police departments, law enforcement officers, and evidence custodians can learn a lot from the real-life cases of mishandled or lost physical and digital evidence. But, what if the integrity of the evidence is compromised despite the fact that your police officers and your evidence management unit did everything right?

Above, we wrote: We all know that mishandled, damaged, or lost physical or digital evidence can happen at any time during the chain of custody: at the crime scene, during the packaging, when transferring, while in storage, and even during analysis.

We re-posted it here to make a very specific point; a point that can’t be made without referring to the lyrics of an old song from Sesame Street. 

One of these things is not like the others,

One of these things just doesn’t belong,

Can you tell which thing is not like the others

By the time I finish my song?

The point we’re trying to make (weak as it may be), is… there is one step in the evidence management lifecycle that the people in your police department are not directly in charge of… analyzing evidence.  

In an article called, Inaccurate forensic evidence can have steep consequences for the accused, they wrote, “Forensic evidence is often viewed as reliable, but errors and associated wrongful convictions may occur due to mistakes, unproven techniques, or misconduct.

Forensic evidence is often treated as a source of objective and accurate information in criminal cases. This evidence may even be decisive in cases in which people have been accused of violent crimes or sexual offenses. Unfortunately, this evidence isn’t always as accurate as people believe.

The Innocence Project states that nearly half of people exonerated on the basis of DNA evidence were originally convicted based on forensics. Many of these wrongful convictions may have involved errors, misconduct, or scientific techniques that were not properly tested and reviewed. Sadly, regardless of the underlying factors, these evidence errors often have devastating consequences for the wrongly accused.


The gravity of these errors was recently underscored when the FBI conducted a review of criminal cases involving hair microscopy evidence. According to The Washington Post, the FBI looked over 500 cases that FBI analysts testified to and reported the following disturbing findings:

Three of the reviewed cases involved people who were charged in North Carolina. In one of these cases, a man is now serving life in prison after being convicted of charges of rape. The man was convicted on the basis of hair evidence that would not even be considered admissible today.

During the man’s trial, an FBI analyst testified that the chances of the analyzed hair belonging to someone else were 1 in 1,000. There is no accepted research to support this assertion, and the recent FBI review concluded that this statement was not scientifically accurate. The man is now pursuing a new trial. Sadly, there may be many other people who have also served time after being convicted based on questionable evidence.


The type of evidence that the ongoing FBI review is focusing on is no longer used to support criminal charges. Still, the findings have troubling implications. The accuracy issues that the review has uncovered may occur with many types of forensic evidence.

The Innocence Project explains that forensic proofs are often presented in trial as fully accurate. In reality, some methods, such as firearm tool mark analysis, have not been verified as scientifically reliable. Techniques that are considered accurate, such as DNA testing, can also yield incorrect results if analysts make mistakes. Intentional misconduct on the part of analysts, although rare, is also a danger that should be taken into account.

Together, these factors can create a significant risk of wrongful convictions, which is a possibility that should not be overlooked during criminal cases.”

When researching the Innocence Project, Tracker found a related article called, Overturning Wrongful Convictions Involving Misapplied Forensics. 

In it, they wrote, “The Problem: The misapplication of forensic science contributed to 52% of wrongful convictions – in Innocence Project cases. False or misleading forensic evidence was a contributing factor in 24% of all wrongful convictions nationally. That was according to the National Registry of Exonerations, which tracks both DNA and non-DNA-based exonerations.

This includes convictions based on forensic evidence that is unreliable or invalid and expert testimony that is misleading. It also includes mistakes made by practitioners and in some cases misconduct by forensic analysts. In some cases, scientific testimony that was generally accepted at the time of a conviction has since been undermined. There have been new scientific advancements in disciplines including:

Hair comparisons

Microscopic hair analysis involves comparing hair found at a crime scene with the hair of the defendant. A 2009 NAS report stated that microscopic hair comparisons could not be used to match hair with a specific individual.

In 2015 the FBI announced that its hair microscopy experts overstated the probability of a match between hair evidence and the defendant’s hair in 95 percent of the 268 cases it had reviewed.


Two decades of fire research have debunked evidence that was used to convict people of arson. The 1992 publication of National Fire Protection Association (NFPA) 921 noted that many of the physical artifacts previously thought to occur only in intentional fires—such as “alligatoring” of wood, crazed glass, and sagged furniture springs—could actually occur in accidental fires. NFPA 921 only became generally accepted by the relevant scientific community in the early 2000’s.

Comparative Bullet Lead Analysis

Comparative Bullet Lead Analysis was believed to link bullets found at a crime scene to bullets possessed by a suspect. But, that was based on the assumption that the lead composition in a bullet was limited to the batch that it came from. Since the early 1980’s the FBI conducted bullet lead examinations in over 2,500 cases. The FBI stopped using CLBA after a 2002 National Academy of Sciences report found problems with interpretations of the results.

For more information click here.

Challenges in Getting Back into Court When Science Changes

Because shifts in scientific understanding often take decades to emerge, individuals whose wrongful convictions were based on misapplied science might face difficulties in proving their innocence due to time limitations and high evidentiary standards. In addition, some state courts do not recognize discredited scientific evidence as new evidence of a wrongful conviction.

It’s critical that there’s a mechanism for the wrongfully convicted to get back into court to prove their innocence. Especially if the forensic evidence to convict them is undermined by new scientific advancements, guidelines, or repudiation of expert testimony.

Case in Point: Pennsylvania Man Originally Denied Access to DNA

In May of 1987, Bruce Godschalk was convicted of rape and burglary in Pennsylvania. The conviction was based primarily on eyewitness identification and a confession later proven to be false. Forensics techniques available at the time of the trial, tested the semen from the crimes, but could not exclude Mr. Godschalk as the perpetrator.

Following his conviction, Mr. Godschalk petitioned for access to DNA testing and was denied. After contacting the Innocence Project in 1995, the District Attorney refused to allow access to the DNA evidence. It was not until November of 2000 that a Federal District Court granted access to the DNA testing.

Delays in testing protocols, delivering the evidence, and legal hurdles, deferred testing of the evidence until January of 2002. Mr. Godschalk was eventually excluded as the donor of the semen in the crimes and released from prison. 

Mr. Godschalk had spent seven of his fifteen years of incarceration fighting for access to DNA evidence. As a result of Mr. Godschalk’s case, Pennsylvania introduced and later passed a law creating access to DNA evidence.

Today every state has enacted a post-conviction DNA statute because the traditional appeals process was often insufficient for proving a wrongful conviction. Prior to the passage of post-conviction DNA laws, it was not uncommon for an innocent person to exhaust all possible appeals without being allowed access to the DNA evidence in his case.”

***But, there are still some shortcomings with these laws. To learn more, Click Here. 

With the laws as ever-changing as they are, it’s incredibly important that evidence custodians consider reviewing and/or updating their policies and procedures, to accommodate the new local and national evidence policies. 

Evidence Management Best Practices are never a once-and-done project. The best evidence custodians we know,  use world-class technology to protect and manage the evidence in their units. They are also committed to ongoing education and connecting with the evidence management community.

By doing these things (and so much more), they can rest easy. Knowing that even if the wrong person is convicted, it wasn’t because of their police department’s protocols. 

Tracker Products and The Evidence Management Institute want to contribute to your ongoing education through… a series of FREE online evidence management training classes. Watch and comment on the Tracker Products webinars here. Check out The Evidence Show! Or – to get in on the discussion, with nearly 800 evidence custodians – join the Evidence Management Community Forum on Facebook. 

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