Today, as yesterday, the prosecution in the trial of Juan Mendez, Jr., (Fort Myers, FL) put “chain-of-custody” witnesses on the stand. Among these was a criminalist who detailed her findings of footprints in and around the crime scene.

TruTV’s commentators debated whether this evidence was at all damaging to the defense. Yet bloody footprints are a staple of classic detection (fictional and otherwise). Why shouldn’t they be damaging in the Mendez murder case?

Debating Facts v Opinion

I think I finally figured something out about trial lawyers: they don’t believe in facts, only opinions. Lawyers think that facts can always be disputed.

Lawyers must learn in school how to debate facts as if they were merely opinions.

In high school I, too, learned how to debate. I joined the Forensic Society (now the National Forensic League). No, it wasn’t a club for geeks who dusted their lockers for prints. It was the debate club. In that club I learned how to debate opinions—using facts to support my opinions. That’s very different from what lawyers seem to learn in school.

• Sidebar: If you look up the word “forensics” at www.Dictionary.com, you will learn that the word still means “public debate.” It does not mean something like “the science of solving crimes,” although before long I suspect it will. The most likely reason “the science of solving crimes” has become “forensic” is that “science” was injected into the courtroom by the U. S. Supreme Court in 1993 in Daubert v Merrill. In that decision the Supremes attempted to remove the possibility of “junk science” creeping into evidence. I think they actually did something else. It’s the “law of unintended consequences” at work again.

Forensics in Court

The Supremes attempted to interject scientific facts into the system—with the best of intentions.

Guilt or innocence is fact. Unfortunately, trial lawyers treat the issue of guilt or innocence as if it were an opinion, not a fact.

All that can legitimately be debated in court is the validity of the evidence of guilt or innocence.

What most of us think of as forensic science is not science: it is craft. I’m not going to call it junk, because much of it is based on interesting and significant phenomena, which can be used by detectives to track down the bad guys—such as bloody footprints.

Forensic-science evidence is only as good as the expert witness who interprets it, though. Interpretation is an art, not a science. (I would have called forensic science an “art,” but that has frivolous connotations, rather like the art of writing fiction.)

Interpretation is very subjective. And some types of analytics are so subjective as to be junk science. Take “footwear-impression analysis,” for example.

The Forensic Science of Footwear-Impression

In the next few days, I expect we will hear from an expert in bloody footprints in Florida v. Mendez. This may well be someone from the FBI Lab. He—or she—will attempt to identify the maker of the shoes that the killer was wearing and to match the size with Mendez’s shoe size. It won’t really mean a thing: the identification will be evidence, but not fact and certainly not proof of anything other than someone walked through the blood of his victims.

• Sidebar: I predict that when the expert makes a “match” he won’t say he made a match. He will say he “cannot exclude the defendant’s shoe size” as the size of the prints, and he will do so “to a reasonable degree of scientific certainty.” (Give the jurors a break!)

Unfortunately, as in the first O. J. Simpson trial, unless the shoes are unique (e.g., rare, expensive, manufactured only in the first half of 2006) and the prosecution has a photo of Mendez wearing such a pair of shoes, then the expert’s analysis will be meaningless.

Florida v Mendez

In fiction, the detectives who first investigate a bloody crime scene would “follow the bloody footprints” to the killer. (Try a Google search—it’s a staple of mystery novels.)

An abusive husband who was under a restraining order would be my first suspect. I would get a search warrant for his house and person—seize all his clothes—search his sink drains for blood evidence. If his only pair of sneakers was missing, I would ask him what happened to them; and if they were sitting in his closet, I would seize them. Wouldn’t you? Apparently the Florida cops didn’t in the Mendez case.

So, the lawyers on TruTV and the ones in court may continue to debate the meaning of the bloody footprints—whether or not the jury will care—but “footwear-impression analysis” isn’t science.  Face the facts. The only bloody footprints that count are the ones that lead directly to the murderer.

Oddly enough, in Florida v. Mendez, apparently the only place the bloody footprints led was to the porch where a toddler in a highchair spent the night outside.

I suspect these are the only bloody footprints about which the Mendez jury will deliberate.