Justice and Science — “Houston, We Have a Problem!”


It’s abundantly apparent that the nature of ‘evidence’ and ‘expert testimony’ has become increasingly more scientific as the decades have rolled by.  And this is a wonderful thing, because real science is a tool for discerning the real truth and the real facts.  It means that “junk science” forensics will ultimately give way to technologies and disciplines founded upon true science, and this is what the NAS Report was all about.

However, the continuing trend for evidence and testimony to become more scientifically based brings with it some “interesting” consequences of which we need to be aware — the impacts on juries and on judges & attorneys; and whether these people are prepared to cope with all this new scientific information and discipline.

We’ll cover the issues in three sections: Juries, Judges & Attorneys, and Experts.


Let’s start with juries.  Potential jurors are selected from the general populace, most commonly with names being taken from voter registration roles or driver’s license records.  How well qualified is the randomly selected citizen to deal with technical and scientific detail?  Not very.  The enrollment in courses pursuing mathematics, physics, chemistry, biology, and engineering has been steadily declining in this country, and I would venture to say that the general populace has been steadily becoming increasingly ignorant of science and technology for decades.  The US ranks behind 14 other developed countries on measured scientific literacy (Program for International Student Assessment).  So it can be expected that the randomly selected US citizen would not have adequate scientific literacy to, on their own, understand highly scientific testimony or evidence, much less be able to make a decision based upon it.

There is a process that is part of jury selection called voir dire.  This is when the prosecution and defense interview potential jury members to determine suitability for being seated on the jury for any particular trial.  Potential jurors may also be asked to fill out a written questionnaire as part of this process.  If it’s known that the testimony and evidence in a trial is going to be highly technical and scientific, each side might try to screen for jurors who are capable of comprehending the evidence and testimony to be presented.  However, as we’ll see in the next section, lawyers are ill prepared to assess someone’s scientific literacy.  Additionally, when jurors are being selected from a pool of people that has been statistically destined to be a group  that is scientifically illiterate, it’s highly unlikely that more than a few, if any, scientifically literate people could be seated on any particular jury.

Driving home this point, there is currently a case in Canada, involving the murder conviction of a retired judge, which turned on the jury’s analysis of scientific evidence.  The Montreal Gazette quotes defense lawyer Jacques Larochelle as saying, “The weakness of a jury in assessing scientific evidence is notorious.”

So where does this lead us?  It leads to having juries being dependent upon “expert” witnesses to explain the science to them in an understandable manner such that they are able to arrive at a decision concerning guilt or innocence.  But expert witnesses bring with them their own set of issues, which we’ll discuss in the final section.

Judges and Attorneys

Judge Richard A. Posner of the US Seventh Circuit Court of Appeals recently issued a decision in a case that involved wrangling over the meaning of scientific evidence.  His opinion was that protracted and unnecessary delay was caused by the inability of the players (judges and lawyers) in the legal system to cope with science; as he viewed the actual legal decision to be made to be trivial.  Writing for the court on 10/28/13, he cited a number of quotes from the literature that make the point well.  You can read Judge Posner’s full decision here: Posner Decision

David L. Faigman, Legal Alchemy: The Use and Misuse of Science in Law xi (1999) – “the average lawyer is not merely ignorant of science, he or she has an affirmative aversion to it”.

Peter Lee, “Patent Law and the Two Cultures,” 120 Yale L.J. 2, 4 (2010) – “As a general matter, lawyers and science don’t mix.”

C.J. Rehnquist, (concurring in part and dissenting in part), U.S. Supreme Court, Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579, 599 (1993) – “the various briefs filed in this case … deal with definitions of scientific knowledge, scientific method, scientific validity, and peer review—in short, matters far afield from the expertise of judges.(emphasis added)

David L. Faigman, et al., Modern Scientific Evidence: Standards, Statistics, and Research Methods v (2008 student ed.) – “law students as a group, seem peculiarly averse to math and science.

It’s clear that judges and lawyers, just like jurors, must depend on expert witnesses to explain and interpret the science and technology of the evidence in the case.  But there are some potentially big problems with experts.

The Problem with Experts

An expert witness is a person, who because of  education, skill, training, or experience is considered to have specialized knowledge and expertise in a particular subject beyond that of the average person, to the point that others may legally rely upon the witness’s “expert” opinion.  It is common for both prosecution and defense to have to agree on the expert status of a witness, but either side can challenge, and the ultimate decision is at the discretion of the judge.  Other than that, there are no special requirements.

Unlike normal witnesses, the expert is not constrained to testifying to matters of fact.  They are allowed to testify as to their opinion and to draw conclusions.  Here is what the Federal Rules of Evidence, Rule 702 has to say about how an expert can testify – “A witness who is qualified as an expert by knowledge, skill, experience, training, or education may testify in the form of an opinion or otherwise.”

Now, “expert” witnesses are just like everybody else in that they all have their own personal collections of internal biases and  beliefs.  So, while they may be testifying about what should be scientific fact, they are allowed to interpret the facts and express opinions and draw conclusions.  This can be very problematic, particularly in expert medical testimony where there may be different schools of thought within the profession about certain subjects.  We see this routinely in SBS (shaken baby syndrome) cases, where a doctor’s testimony will be driven by his/her own personal biases about the issue, and he/she is allowed to express his/her opinion.  And is it possible that an expert can be flat-out wrong?  Absolutely.  Case(s) in point would be the years of erroneous expert testimony by FBI agents about the subjects of compositional analysis of bullet lead and microscopic hair comparison.  And then there’s the decades of scientifically incorrect arson junk science expert testimony by arson investigators who did not understand, or did not accept, what science has discovered about the markers that set fires do, or do not, leave behind.

Scientifically illiterate lawyers, whether prosecution or defense, are not capable of challenging the details or conclusions in the testimony of an expert.  The best they can do is produce an expert of their own to provide contradicting testimony.  This happens commonly, and leads to the situation I call “dueling experts.”  Witnesses that have been sanctioned by the court as “expert” are providing opinions that are polar opposites.  So what the hell is the jury supposed to think?  They’re dependent on the experts to understand the evidence, but now they’re being presented with diametrically opposing opinions by two (or more) different “experts.”  Unfortunately, what usually happens in this situation is “majority rule.”  Whichever side, prosecution or defense, can produce the most experts will likely sway the jury.  I’m aware of an SBS (shaken baby syndrome) case in which the prosecution’s experts outnumbered the defense’s by 9 to 1.  And considering that expert witnesses cost money, guess who always wins the battle of producing the most experts?   Of course – the prosecution.  It’s justice for sale, and it dramatically favors the prosecution, because they can afford it.  Or it may be that the expert who is the more “dynamic” presenter, regardless of whether or not he/she is correct about the science, will be the one who influences the jury.  Clearly, this takes the trial out of the realm of logic, facts, and science and turns it into “theater.” (And very unfortunately, by the way, lawyers have honed this strategy to a fine theatrical art; playing to the emotions and biases of the jury whenever they can.)


I wish I had a solution to the problems presented by these issues, but I do not.  We’re certainly not going to be able to turn jurors and judges and lawyers into scientists.  Perhaps a part of the solution may be to invent some way of ensuring the integrity and accuracy of experts.    However, my mission here has only been to raise awareness of the issues so the players in the justice system, including defendants, may be a little more prepared to cope with them when they arise.  Forewarned is forearmed.

4 responses to “Justice and Science — “Houston, We Have a Problem!”

  1. I always appreciate your articles, Phil!

    I think the expert testimony has gotten out of control. It comes down to which side has the most money to pay for the experts. In may cases, the defense can’t afford to present a counter to all of the State expert witnesses so it ends up being very unfair. I agree that biases also come into play and some “experts” are known as liars for hire.

    I think jurors need to try to put all of the forensic evidence aside and use common sense first. “Does the State’s theory work?” Consider the Camm case with so much expert testimony about blood spatter. Putting that aside, the jury only needed to consider how strong his alibi was with 11 witnesses seeing him playing basketball at the time of the murder. That should have been given much more strength as evidence than the blood spatter evidence and I believe it was in the 3rd trial and he was finally acquitted.

  2. Pingback: Justice and Science – A Problem |

  3. I’ve often thought a revealing question the defense should ask, which any juror can understand, is this: How many times have you testified as an expert witness? And how many times did you testify for the prosecution? And how many times for the defense? If a expert had testified 100 times and 100 of them were for the prosecution, would not this cast a huge shadow on their objectivity? Many should be seen as what they are: mercenaries for the prosecution. Nothing more.

  4. Having used a very qualified forensic expert witness in a case, it is the qualification of the expert that should determine the weight of their testimony. A well qualified expert is just that an expert – otherwise an ill prepared, unqualified expert is no better than an unqualified coroner or prosecutor. Neither should be on this case.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s