In 2001 Marcellus Williams was convicted of first degree murder. The 42 year old female victim had been stabbed 43 times in her St. Louis home. No DNA evidence was available at that time and Williams was convicted based primarily on the testimony of two convicted felons. Now DNA from the murder weapon and  hair samples found at the scene are available, and it appears that DNA does not match Williams but is a match for someone else. The State of Missouri still planned to execute Williams last night.

Yesterday, Republican Governor Eric Greitens issued a stay of execution until the case can be examined by an independent body. In issuing the stay Greitens said: “To carry out the death penalty, the people of Missouri must have confidence in the judgment of guilt”.  Well…yeah. But there is often a problem with that whole “confidence in the judgement of guilt” thing.

In 2016 149 people were exonerated and freed from American prisons after being incarcerated an average of fifteen years for crimes they did not commit. Some of these were for drug offenses and other felonies, but 54 were convicted murderers, five of whom were on death row awaiting execution. Many of those 149 were young or were mentally handicapped at the time of their conviction.

There is no way to know exactly how many people currently sitting in jail or prison are actually innocent. If you ask the prisoners I’d bet you would learn that almost all are, but I’d have trouble trusting their honesty! However, mathematical modeling by the National Academy of Sciences concludes that based on the percentage of prisoners exonerated over time we could anticipate that at least 4.1% of people currently in prison convicted of murder are innocent.

Those convicted of crimes other than murder are also a concern. The University of Michigan’s Exoneration Registry reported that 891 people convicted and serving time in prison were set free in a 13-year period beginning in 1989. And these are only the cases that were proven by The Innocence Project and other non-profit groups; one must assume other innocents were not exonerated.

So let’s just go with that 4.1% estimate and assume it applies to people convicted in American courts. Approximately 2.3 million Americans were incarcerated in 2013, the last year federal data were  available, and about 6.9 million adults were under the supervision of a corrections system, either actually incarcerated or under control of  probation or parole. Yep. That’s a lot of people convicted of crimes. So even if 1% of those found guilty are innocent that would be 69,000 wrongful convictions. If the 4.1% figure is accurate there are more than 282,000 innocent Americans currently under the control of local, state, or federal corrections systems.

Again, these are just estimates. I’m just making up numbers. It is impossible to know whether they are accurate. But what if they are? What if the number is even higher? Does it matter if the number is much lower if we know we have innocent people spending time in prison or being executed? What if it is only a dozen? If I’m one of that dozen it sure matters to me.

So why am I confident at least a portion of Americans convicted in court are innocent? Well, I’ve been studying courts and teaching classes on court structure and procedure for more than three decades, but I’m sure you want more evidence. You can watch this episode of Adam Ruins Everything for a sort of lighthearted approach to the subject. Adam will probably be more interesting than what I have to say, but if you insist…

In 2009 the Florida Supreme Court created the 23 member Florida Innocence Commission to determine why the state had a high rate of wrongful convictions. The Commission released its report in 2012 and listed several reasons innocent people are convicted, and the Commission’s conclusions are relevant to all American courts.

Here are the major problems identified:

• Unreliable jailhouse snitches. Remember Marcellus Williams? He was convicted based on the testimony of two jailhouse snitches. This is a problem in about 15% of wrongful criminal convictions.
• Eyewitness misidentification. It is estimated that eyewitnesses misidentify criminals in about 75% of the cases that are later overturned using DNA evidence. This piece in Scientific American explains why memory is not accurate. In fact, eyewitnesses often create false memories. Unfortunately juries really rely on eyewitness evidence.
• False Confessions. A large number of innocent people have spent a lot of time behind bars because of false confessions. This often is the case when young people or those with limited intellectual abilities are subject to aggressive interrogation. They may be intimidated by authority or have other immature reasoning abilities.
• Invalidated or Improper Scientific Evidence. Science is awesome, but it is often incomplete or overstated. In other words scientific methods used in criminal convictions often lack complete validity or are exaggerated by prosecutors. Examples of less reliable forensic evidence are bite marks (very unreliable), tire treads, fiber evidence, and hair matching. Or to be clearer, these have not been subject to thorough scientific validation, so we cannot be certain they are valid. DNA evidence is highly reliable but is often unavailable.
• Professional Responsibility and Accountability of Both Prosecuting and Defense Attorneys. Attorneys are bound by state ethics codes but they also work in a system that expects them to do everything they can to win their case. Need I say more?

The Commission also found that an overarching problem was that the entire criminal justice system was underfunded. Prosecutors and public defenders often deal with unmanageable caseloads, crime labs are underfunded, court-appointed attorneys are paid less than they should be, police are under paid, and more.

So the bottom line? It is almost certain that an indeterminate number of people currently sitting in a prison cell or under the watchful eyes of the pardon and parole system are innocent. At least some of those folks are either serving life sentences or are awaiting execution in one of the 32 states still using the death penalty. Being wrongfully incarcerated is unacceptable. Being executed for a murder one did not commit is, in itself, criminal.

I oppose capital punishment for personal/spiritual/philosophical reasons, but not everyone shares my personal views. However, we should at least be able to agree that executing people who are innocent is unacceptable, and I believe we almost certainly have done so in the past and will do so again as long as we rely on a fallible human institution to convict people accused of crimes.

I’m glad Governor Greitens appointed a panel to review evidence used to convict Marcellus Williams, but even after that review we will not know for certain whether he is guilty or innocent. That group of five people will have an opinion. Is that enough to justify taking someone’s life?