It was 1985 and Robert Lee Stinson was on trial for the murder of his neighbor.
“She was the 63-year old widow found dead near the corner of 7th and Center streets.
The crucial evidence in this case is bite marks found on the body of the victim.”
Two forensic dentists said the bite marks matched Stinson’s teeth, but there were
some puzzling discrepancies.
They claimed Stinson’s broken tooth made this mark even though there was no mark for
the adjacent, full-size tooth.
And when they were called to testify in court, nobody asked them about that.
“The bites had to have been inflicted by dentition identical to Mr. Stinson's.”
Stinson’s trial was a test of whether our criminal justice system
was capable of detecting unreliable forensic science.
And with the future and freedom of a young man on the line,
the result was an absolute, system-wide failure.
The US has an adversarial judicial system where the judge presides over a trial but isn't
responsible for uncovering the truth.
Instead, it's up to the opposing lawyers to present evidence and witnesses that support their
version of events.
“Ultimately the theory is of course that through this conflict of ideas and interpretations the
truth will emerge.”
But from the start, Stinson could tell he wasn’t entering a fair fight.
He prepared a letter asking for a replacement for his lawyer, who “only took his case
two weeks” before trial.
“Your Honor, I’m facing life for something I did not commit,” he wrote.
The judge denied his request, which came in the middle of the trial,
and she also denied his lawyer’s motion to exclude the bitemark evidence.
She said “there are adequate standards and controls in the area of forensic odontology.”
“It is a recognized area of science.”
"Frankly at the time it was not a close decision for me.
Even though it was unique testimony, I didn't have anything in front of me that indicated
that it was not reliable and it certainly was helpful to the jury, I think, and relevant
to the issues and so I admitted the evidence."
At the time, Wisconsin only required that forensic testimony be relevant and helpful
to the jury.
Judges weren’t required to assess its reliability.
“You have an older woman who's been raped and murdered and we've got an expert who's
saying we know who did it.
If the judge excluded that evidence he would gone free.
And it would have been a legal stretch for her to do that given the state of the law
and the precedent at the time."
As the appeals court would point out in a footnote, by the time of Stinson’s trial,
bitemark evidence had been accepted in 19 jurisdictions and rejected by none.
The court in Stinson’s case was no different, and the bitemark evidence went before the jury.
The first thing that happens when forensic experts take the stand is that they’re prompted
to list their credentials, to show that they’re qualified.
“That makes sense from a certain perspective.
But there's also a danger that the jury misunderstands the power of that experience.”
“Dr. Johnson seemed to make sense to me when he testified.
He certainly was qualified,
being a professor at the university in the dental school."
“Here you have this very learned
dentist who has no reason to lie who comes in and tells you this is rock solid science.
How is the jury to decide he must be wrong?
That's extremely compelling.”
Dr. L.T. Johnson walked the jury through the evidence.
He even brought models of Stinson’s lower teeth and one of the bite marks
so he could show how they matched.
He concluded his testimony by saying the bite marks
“would have to have been made by Robert Lee Stinson.
The second dentist, Raymond Rawson, testified that
“there was no question that there was a match to a reasonable scientific certainty."
Stinson’s lawyer did try to get a defense expert of his own, but that expert was never
called to counter the prosecution’s dentists in court,
because after he examined the evidence,
he agreed with them.
Instead of two sides battling it out before the jury, there was one side with two experts
making false statements about the science, and one side with no experts at all.
During Stinson’s trial, the prosecution and defense would ask the two bitemark experts
a combined 240 questions.
But they didn’t ask the most important one.
“The real question that we should be asking is what is the evidence that shows us that
people in this field reach accurate results?
It's not rocket science.”
Forensic scientists can have protocols and guidelines, use well-accepted tools and technology, but
we won’t know if their methods are actually reliable until we have what’s called an
“error rate study.”
You take a bunch of bite mark examiners, give them samples of bite marks and then measure
how often they make a correct identification.
To this day, nobody has ever conducted a proper error rate study for bite mark analysis.
“And there's really no incentive to do any research, because courts admit it.
If courts stopped admitting it they would do the research, right, because they want it
to be introduced at trial.”
Studies that have been done with human cadavers show that there’s a lot of distortion when
bite marks are made in skin, even in a laboratory setting.
The same set of teeth will make marks of different sizes and shapes depending on the skin type,
the amount of force, and the orientation of the bite.
Missing teeth can look like they’re there.
Teeth that are there can look like they’re missing.
One study conducted by forensic dentists found an unsatisfactory level of agreement among
examiners on whether a given injury was even a human bitemark.
But during Stinson’s trial, Dr. Johnson told the jury that there was “no margin for error"
in this case.
And then Stinson took the stand.
He said he was at a party until about 12:30.
Went home, and then later went back out, to go to the store with a friend.
He said as they walked behind his house, he heard footsteps and shushing coming from the
back of the alley.
But when Stinson first spoke to the police three days after the murder, he had only told
them he went home after the party and went to bed.
As the prosecutor pointed out at the trial, he had changed his story.
“It's my experience that the jury looks a lot at those alibis and if somebody is lying
for no other reason then perhaps trying to get out of something, that is pretty heavy evidence."
After a three-day trial, and less than two hours of deliberation, the jury found Stinson
guilty of first degree murder.
And he was sentenced to life in prison.
On appeal, Stinson challenged the admissibility of the expert testimony in his trial.
But the Wisconsin Court of Appeals affirmed his conviction.
They were impressed by the dentist's elaborate methods.
"Doctor Johnson used an ' Acrylic ring.'
'Special camera.'
'Three dimensional indentations.'
'Overlay technique.'
'75 individual tooth marks.'
They actually claimed
"the reliability of the bite mark evidence in this case was sufficient to exclude to a moral certainty
every reasonable hypothesis of innocence."
“It's so absurd.
Tarot card readers have a very complex ancient methodology.
It doesn't mean that they can tell your fortune.”
And with that ruling, Stinson became the precedent-setting
for bite mark evidence in Wisconsin.
Seven years later, the US Supreme Court issued a decision -- the Daubert ruling -- which
should have changed the entire landscape for forensic science.
It said that trial judges must assess whether expert testimony is based on reasoning or
methodology that is “scientifically valid.”
Daubert talks about reliability, validity, empirical data, error rates, peer review.
It has all the good stuff and scientists would look at it and feel their hearts would patter,
they'd be cheered, because it says all the right words.
But the problem with that is it also says it's a flexible standard.
The Daubert ruling gave judges a new “gatekeeping role,” but at the same time, it said that
“vigorous cross-examination and presentation of contrary evidence” is still an “appropriate
means of attacking shaky but admissible evidence."
So even though judges are supposed to evaluate expert testimony, they can still choose to
offload that responsibility.
“They don't want to be responsible for letting the killer go free because they excluded the evidence."
After all, the system has always relied on the attorneys to cross-examine witnesses they
disagree with and present contrary evidence.
“Public defenders are by and large overwhelmed and often don't have the funding to hire their
own independent experts.
I mean but they shouldn't have to.
We shouldn't have to be defending against unreliable scientific evidence.”
And ultimately, it’s up to the jury to decide what they believe.
“I mean the instructions are very clear that the jury does not have to give any further
weight to an expert than any other witness.
What kind of weight they want to give to them is totally up to them.”
But the jury doesn’t have basic information about the error rates of forensic methods
like bite mark analysis.
Those studies don’t exist — in part because judges have never required them.
“I don't think there is evil intent anywhere in this circle.
It's a collection of institutional participants sometimes taking the easy way out."
“Nothing is suitable in our existing system for making the scientific determination
that this evidence is questionable.
And here's what juries and judges ought to know about it.
It's not happening.”
As Robert Lee Stinson began his life sentence, the evidence in the case was boxed up and
locked away.
That included the blue pullover shirt the victim was wearing when she was killed.
It was a crucial piece of evidence, but nobody knew that yet.
And it would be 24 years before the true killer was found.