Skip to main content

Junk Science Sends the Wrong People to Prison

Bite marks
There are five reasons and even more causes that lead to wrongful convictions.

What causes wrongful convictions? As I posted recently, it comes down to about five reasons (although as the National Registry of Exonerations points out, many cases have multiple causes):

Highest in adult sexual assault cases (31%) and homicide (23%), false or misleading forensic evidence can be just as vexing an issue as false confessions, due primarily to the CSI Effect. Documented as far back as 2004, the phenomenon can cause issues for prosecutors and defense attorneys alike, by giving juries unrealistic expectations as to the capabilities of crime labs.

What are we talking about when we say the evidence is false or misleading? It could be a number of things. There have been cases where evidence was planted by investigators. Those are presumably rare, and I’m not certain how NRE considers planted evidence. Does it fall under this category or Official Misconduct? Examples such as the 1993 New York State Police Troop C scandal are particularly egregious.

This category could cover a number of issues, but here are four major areas of concern.

Bite Marks


Radley Balko has written extensively on the junk science behind bite mark evidence. The idea is that forensic dental specialists can match bite marks on a person or body with a copy of the accused person’s teeth and do so with some high degree of success, because in theory, human dentition is unique, and human skin can register and record that uniqueness in a useful way.

The reality of the matter is that human skin is a horrible medium for preserving indentations and marks like bites. It stretches during the bite, and may or may not go back to its original shape. But more importantly, it hasn’t been proven that human teeth are as specifically identifiable and unique as fingerprints or DNA.

It’s one thing for a forensic odontologist to take a specific jaw or skull and compare it to a specific set of medical records in an effort to identify the skull or jaw. You’re comparing one objective thing to another. The medical record shows fillings in these three positions; the suspect jaw shows three fillings in the same position. X-rays of the fillings appear to match. The tooth counts match. That’s a fairly straight-forward process and pretty objective.

Bite-mark matching is a bigger issue though. Before the mark can be compared to a suspect’s teeth, it must first be identified as a bite mark, and one made by a human. While that sounds easily done, a survey by the American Board of Forensic Odontology – the group that certifies bite-mark examiners – found a distinct lack of agreement on whether individual bites were of human origin. The group surveyed 39 examiners, giving them the same 100 bite mark photos and asked three basic questions:

Is there sufficient evidence in the presented materials to render an opinion on whether the patterned injury is a human bite mark?

Is it a human bite mark, not a human bite mark, or suggestive of a human bite mark?

Does the bite mark have distinct, identifiable arches and individual tooth marks?

By the time the examiners worked their way through the process, they only agreed on 4 of the 100 photos. 4 %.

People are being sent to death row on the basis of bite mark evidence, and 39 certified examiners can’t come to an agreement on known examples. That should indicate some sort of problem, but the ABFO seems more interested in processes than results. The situation will not change until the ABFO makes it a priority. Until then, the best anyone can do is to keep trying.

Hair Analysis


DNA test
This is the yang to the yin of bite-mark analysis. Both forensic tools revolve around subjective, pattern-based forensic techniques. We’re not talking DNA samples from hair here, but rather comparing two separate hairs, and saying they came from the same person. The FBI estimates as of a year ago that FBI hair examiners have given flawed testimony in over 95 % of the cases examined. 32 of those cases were death-penalty cases, and in 14 of those cases, the defendant has either been executed or has died in prison.

The Justice Department announced in February 2016 that it would expand its review of pattern-based forensic techniques, which include bite-mark and hair analysis as well as firing-pin impressions, shoe treads, and fiber evidence. I suspect we’ll be hearing about more exonerations as that review continues.

Arson Investigation


For years, many arson investigators have learned “on-the-job” from previous investigators, and they’ve passed on time-honored knowledge about the telltale signs of an arson fire. These typically included nuggets of wisdom such as, “Crazed glass in windows shows it was a very hot fire, and that means it was arson.” But that’s since been determined to be false. It’s not rapid heating that causes glass to craze, it’s rapid cooling, such as might occur when a hot glass gets hit with cold water from a fire hose.

The investigator who determined that Cameron Willingham had set the fire that killed his three girls testified that he had investigated over a thousand fires in his career, and every single one of them was an arson fire. All of his knowledge came from hand-me-down ideas like this before science really understood how fire worked, and what a flashover was, and what kind of damage it causes. But all of his knowledge was based on false assumptions, so what does that mean for Cameron Willingham?

The NRE lists 26 exonerations that involved arson and false/misleading forensic evidence. That’s about 1.5% of the exonerations. There are probably more to come.

Unqualified Staff


We like to assume that the people conducting investigations and lab tests and autopsies are trained and qualified to do what they’re doing. That’s something of a societal linchpin, isn’t it? That the people who protect us are knowledgeable about their duties and responsibilities?

But what if they’re not? What happens when you’ve got a forensic pathologist performing 5 times the number of autopsies the National Association of Medical Examiners allows and isn’t even board certified in pathology?

What happens when half of your lab staff can’t pass proficiency testing?

Some jurisdictions take drastic measures to fix the problem, as Houston did in 2002.

It’s a national problem though, with cases popping up in New York, Philadelphia, St. Paul, and West Virginia. One judge remarked that the work of the serologist involved was so poor that everything he had done should be considered “invalid, unreliable and inadmissible.”

Now What?


The FBI’s move to expand its review would be an excellent idea if there is official support for the follow-through. We can’t just look at a few cases, determine there’s a problem, then go on with life. The government must, at all levels, be willing to respond reasonably to the issues being raised, actively seek out errors, then promptly remedy those errors and make the victims of those errors whole again. That doesn’t stop with letting them out of prison and wishing them well.

People wrongfully convicted deserve to be compensated for what they’ve lost in life. – but that’s another post.

Source: goodmenproject.com, Bob Mueller, February 26, 2019


⚑ | Report an error, an omission, a typo; suggest a story or a new angle to an existing story; submit a piece, a comment; recommend a resource; contact the webmaster, contact us: deathpenaltynews@gmail.com.


Opposed to Capital Punishment? Help us keep this blog up and running! DONATE!



"One is absolutely sickened, not by the crimes that the wicked have committed,
but by the punishments that the good have inflicted." -- Oscar Wilde

Most viewed (Last 7 days)

Boston Marathon bomber’s appeal of death sentence marked by delays and secrecy

As the city marks the 12th anniversary of the Boston Marathon bombings, Dzhokhar Tsarnaev sits on federal death row for admittingly detonating bombs at the finish line that killed three people and injured more than 260 others. Yet, his fate remains uncertain after a decade of legal wrangling, as his lawyers continue to challenge his death sentence.  The federal judge who presided over his 2015 trial was ordered by an appeals court in March 2024 to investigate defense claims that two jurors were biased and should have been stricken from the panel. If he finds they were, then Tsarnaev is entitled to a new trial over whether he should be sentenced to life in prison or death, according to the appeals court. 

USA | Who are the death row executioners? Disgraced doctors, suspended nurses and drunk drivers

These are just the US executioners we know. But they are a chilling indication of the executioners we don’t know Being an executioner is not the sort of job that gets posted in a local wanted ad. Kids don’t dream about being an executioner when they grow up, and people don’t go to school for it. So how does one become a death row executioner in the US, and who are the people doing it? This was the question I couldn’t help but ask when I began a book project on lethal injection back in 2018. I’m a death penalty researcher, and I was trying to figure out why states are so breathtakingly bad at a procedure that we use on cats and dogs every day. Part of the riddle was who is performing these executions.

Singapore executes man for 2017 murder of pregnant wife and daughter

Teo Ghim Heng, who strangled his pregnant wife and four-year-old daughter in 2017 before burning their bodies, was executed on 16 April 2025 after exhausting all legal avenues. His clemency pleas were rejected and his conviction upheld by the Court of Appeal in 2022. Teo Ghim Heng, who was convicted of murdering his pregnant wife and their four-year-old daughter in 2017, was executed on 16 April 2025. The Singapore Prison Service confirmed that Teo’s death sentence was carried out at Changi Prison Complex. In a news release on the same day, the police stated: “He was accorded full due process under the law, and was represented by legal counsel both at the trial and at the appeal. His petitions to the President for clemency were unsuccessful.”

USA | They were on federal death row. Now they may go to a supermax prison.

A group of federal prisoners filed a lawsuit this week accusing the Trump administration of seeking to move them to a supermax prison to face tougher conditions as punishment for having their death sentences commuted by President Joe Biden. President Donald Trump has repeatedly criticized Biden’s decision to commute the sentences of 37 federal death row inmates to life in prison without parole. After his inauguration, Trump ordered that the former death row prisoners be housed “in conditions consistent with the monstrosity of their crimes and the threats they pose.”

Indonesia | British grandmother who has spent 12 years on death row hugs grandchildren for first time as they visit Bali prison

Lindsay Sandiford, 68, reportedly shared 'cuddles and kisses' with her loved ones for the first time in years A British grandmother who has been stuck on death row in Bali for more than a decade has been reunited with her loved ones for the first time in years. Lindsay Sandiford has been locked up in Indonesia's notorious Kerobokan Prison since 2013 after being found guilty of trying to smuggle £1.6million of cocaine into the country.

Indiana Supreme Court sets May 20 execution date for death row inmate Benjamin Ritchie

The condemned man has exhausted his appeals but is likely to seek a clemency plea. Indiana Supreme Court justices on Tuesday set a May 20 execution date for death row inmate Benjamin Ritchie, who was convicted in 2002 for killing a law enforcement officer from Beech Grove. The high court’s decision followed a series of exhausted appeals previously filed by Ritchie and his legal team. The inmate’s request for post-conviction relief was denied in Tuesday’s 13-page order, penned by Chief Justice Loretta Rush, although she disagreed with the decision in her opinion.

Afghanistan | Four men publicly executed by Taliban with relatives of victims shooting them 'six or seven times' at sport stadium

Four men have been publicly executed by the Taliban, with relatives of their victims shooting them several times in front of spectators at a sport stadium. Two men were shot around six to seven times by a male relative of the victims in front of spectators in Qala-i-Naw, the centre of Afghanistan's Badghis province, witnesses told an AFP journalist in the city.  The men had been 'sentenced to retaliatory punishment' for shooting other men, after their cases were 'examined very precisely and repeatedly', the statement said.  'The families of the victims were offered amnesty and peace but they refused.'

South Carolina executes Mikal Mahdi

Mikal Mahdi, 42, was executed for the 2004 murder of 56-year-old James Myers A man facing the death penalty for committing two murders was executed by firing squad on Friday, the second such execution in the US state of South Carolina this year. Mikal Mahdi, 42, was executed for the 2004 murder of 56-year-old James Myers, an off-duty police officer, and the murder of a convenience store employee three days earlier. According to a statement from the prison, "the execution was performed by a three-person firing squad at 6:01 pm (2201 GMT)," with Mahdi pronounced dead four minutes later.

Louisiana to seek death penalty for child killer despite Biden’s commutation

CATAHOULA PARISH, La. — While a federal death row sentence has been reclassified by former President Joe Biden to life without parole, the State of Louisiana still seeks the death penalty for a man convicted of the kidnapping, torturing and murdering a child in Catahoula Parish.  According to a statement by the Seventh Judicial District of Louisiana District Attorney Bradley Burget, on Monday, a Catahoula Parish Grand Jury indicted Thomas Steven Sanders for the first-degree murder of 12-year-old Lexis Kaye Roberts in 2010. 

Texas executes Moises Mendoza

Moises Sandoval Mendoza receives lethal injection in Huntsville for death of 20-year-old Rachelle O’Neil Tolleson  A Texas man convicted of fatally strangling and stabbing a young mother more than 20 years ago was executed on Wednesday evening.  Moises Sandoval Mendoza received a lethal injection at the state penitentiary in Huntsville and was pronounced dead at 6.40pm, authorities said. He was condemned for the March 2004 killing of 20-year-old Rachelle O’Neil Tolleson.