Scientific evidence is rarely presented well in court. More often, highly technical data is presented in a “dumbed-down” form that lawyers seem to think jurors require. But the biggest problem is that expert witnesses for the prosecution are presumed competent and trustworthy.

Unfortunately, scientists like the rest of us, sometimes make mistakes, are careless, have biases, or are just plain incompetent. Medical examiners are among the expert witnesses most prone to these failings, in my non-lawyer, non expert opinion.

A Medical Examiner Who Works Backwards

The ME who conducted the autopsies in three televised trials exemplifies for me the problems of scientific presentations in court. I think of her as the Serial ME—one homicide after another. She never lets a gunshot death pass for anything but first-degree murder.

The Serial ME turns up on CNN’s In Session frequently, partly because she works in Tennessee, which is among the few states to permit cameras in courtrooms, and partly because she’s photogenic. Unfortunately, she doesn’t “put on a good show,” in my opinion. And she would not appear on TV if it weren’t for the frequency with which she deduces first-degree murder in gunshot deaths.

Trial of John Collett

In 2009 John Collett was charged with murder for shooting an angry, gun-toting trespasser who threatened his parents and him as they stood on their porch. The Serial ME declared the death to be a homicide and testified dramatically with the use of a mannequin, dowels, and the four-wheeler the deceased had driven onto Mr. Collett’s property.

Death by multiple gunshot wounds, of course, must always be investigated as a possible homicide. The circumstances in the Collett case clearly indicated it was not a suicide, and since a hominid must usually pull the trigger on a gun in order for a bullet to emerge from the barrel and find its way into another hominid’s body, a finding of homicide as the manner of death was reasonable.

The medical examiner went beyond this conclusion in her testimony, however. And this is what I find fault with (and apparently the jury did, too, because they found Mr. Collett not guilty). She claimed to prove that the weapon the trespasser waved in Mr. Collett’s face was pointed barrel-to-the-sky when he was shot—based on the trajectory of the bullets in the body. In other words, she testified that she knew for a fact the death was first-degree murder.

In any gunshot death the trajectory of the bullets is an important element of the autopsy evidence. In the Collett trial, the Serial ME demonstrated for the jury the trajectory of several bullets (five, I think) by inserting long dowels into a mannequin that was seated in the four-wheeler (which supposedly wasn’t in itself admitted into evidence). Of course, the path of a bullet through a body is only part of the evidence needed to show the bullet’s trajectory, because a body can be in many positions when the bullet enters it.

Sidebar: How a judge could permit a four-wheeler into a trial court without admitting it into evidence is a mystery to this mystery writer. I would hope that in the event of a conviction the appeals court would have overturned the verdict based on this error alone.

One of the bullets, according to the Serial ME, entered the deceased’s right arm (which was holding a fairly heavy weapon) at the elbow and then passed through the elbow and reentered the upper arm. She also testified there was no way this trajectory could have occurred unless the arm was raised above the head (in other words, she thought she had proved the killing was not in self-defense).

The ME made several assumptions about the shooting, which an autopsy could not possibly suggest, let alone prove.

For one thing, she assumed that one bullet struck the body while the man was still seated on the four-wheeler. That could only follow from an assumption that the bullet was the first one fired. Even if the body was still seated, the trajectory could have resulted from a bullet impacting as the man swung his gun around toward Mr. Collett: imagine holding your arm roughly at waist height with your forearm across your body, bent, and with your elbow at an angle perpendicular to Mr. Collet’s gun barrel.

She also testified that one bullet could only have been fired when the body was already on the ground. Again, she made unjustified assumptions about the order in which all the bullets were fired.

There’s no way an ME can tell the order of most gunshots based solely on the path of the bullets through the body. I suppose some such conclusions can be drawn in some circumstances. If paths cross inside the body or if two bullets follow roughly the same path, it should be possible to conclude that one was fired before the other. But in this case, there were more than two bullets and more than two paths. Blood flow might also prove that a bullet was fired after death, but that was not what happened in this case.

Finally, the Serial ME testified to the rapidity of fire. She concluded that it took a very long time for all the bullets to be fired—implying that each bullet was fired deliberately and with an intent to kill. Yet the gun in question was a semi-automatic pistol that fires rapidly. How could an ME possibly conclude anything about the rapidity of fire in any case?

It was as if the Serial ME wanted to prove the defendant guilty of first degree murder. That’s the prosecution’s job, not an ME’s.

Trial of Eric McLean

Like John Collett, Eric McLean was charged with first-degree murder in Tennessee. His high-school-teacher wife’s teenage lover came onto his property, and Mr. McLean threatened him with a gun (a rifle or shotgun of some sort). In the trial, Mr. McLean claimed he did not intend to pull the trigger; the gun discharged accidentally.

The Serial ME testified there was no way the gun could have discharged accidentally. It had to be intentional. That’s the prosecution’s job, not the ME’s. And, like the Collett jury, the McLean jury did not buy the ME’s claims.

You might wonder how an ME could testify about weapons and ballistics. I suppose she could have based her conclusion on the average muscle strength of the human finger or something.

You might wonder how an ME could infer the intention in the mind of someone who held a gun. I suppose she could have read the defendant’s mind.

Sidebar: I don’t remember all the details of the ME’s testimony, but I think she may have staged a demonstration with the gun in the courtroom in this trial, too.

Trial of Raynella Dossett-Leath

In 2009 Raynella Dossett-Leath was tried for the murder of her husband. The Serial ME testified that the deceased could not have committed suicide for two reasons: 1) he had such a high level of barbiturates in his system that he would have been unconscious when he died, and 2) three shots were fired but the second shot killed him.

The ME’s “Report of Investigation by County Medical Examiner” (dated the day after the incident) is available online. It summarizes the case, but does not include any reference to the drugs in the victim’s system, because (as I understand it) that finding came much later, after a blood sample was sent to the TN state crime lab, which has since lost the blood sample.

The report exhibits the same leap to a conclusion of homicide that the ME made in the Collett and McLean cases.

However, the Serial ME’s role in the prosecution of Ms. Dossett-Leath is so extensive and complex, I need to discuss that case in another blog post.

To be continued …