Bad Science

by D. H. Garrison, Jr.
Forensic Services Unit
Grand Rapids Police Department
Grand Rapids, Michigan

This Article Originally Appeared in the MAFS Newsletter, October 1991.

Forensic science is the product of an uneasy and unholy mating of Science,
the objective seeker of truth and knowledge, and Forensics, the argumentative
persuader of courtroom advocacy. It is not called Justice Science, Law Science,
or Truth Science, as many of us would like to imagine. We are a bastard child,
an orphan, but still the subject of an intense child custody battle between
our estranged parents, the truth seeker and the advocate. The tug-of-war
goes on daily for our loyalties and confidences, each side offering candy
and warm hugs. These separated parents have visitation rights. Sometimes
they take our brothers and sisters away. Sometimes they don’t come back.

We in forensic science like to think of ourselves as our mother’s child–Mother
Science, pure and incorruptible–and most of us start out this way. Some
of us remain pure. Some grow up to be delinquents. The advocacy half of forensic
science will not go away; it has weekday visitation rights and the
power-of-subpoena. It has advocate friends called prosecutors, attorneys,
cops, the press, and the Government. The advocates rarely understand the
appeal of Mother Science, cannot fathom a search for truth in a game plan
which calls for scores and trophies. They are constantly trying to persuade
us to see it their way, to compromise, to bend just a little. They don’t
realize it, but what the advocates are asking for is Bad Science.

The pressure to be a Bad Scientist, to fit in and go along, is great, and
it doesn’t go away unless you put your foot down and say Enough Is Enough!
And keep saying it to each supervisor, each detective, and each fair-haired
boy from the prosecutor’s office. Bad Science is what forensic science becomes
when an attorney or prosecutor, who often display all the ethics of a full-grown
hamster, get a forensic scientist to play ball, to get with their program
and see their big picture. There is an old Bad Science joke about a scientist
who was working with an ant. The scientist would cut off one of the ant’s
legs and shout, “Jump!” And the ant would jump. The scientist cut off a second
leg, told the ant to jump, and again the ant jumped. And so it went, until
the scientist had cut off all six of the ant’s legs. This time, when told
to jump, the ant did not jump. This proves it, the scientist concluded: when
you chop all the legs off an ant, the ant goes deaf!

You may recognize some scenes from the following examples of Bad Science
at Work. Some are laughable, others disturbing. Some simply haven’t happened
to you yet. I have not personally encountered all of these situations, but
I know that each is true. If you haven’t witnessed at least some of them,
you will. If this helps you steel yourself against the onslaught of the
Advocates, so be it. Finally, not all Advocates are malicious. Many, in fact,
are simply not versed in the ways of good scientific method. When they ask
for Bad Science, you can pity them as helpless people doing the wrong thing
for the right reason. This type of Advocate needs to be taught . . . and

Misinterpretation of Test Results

In a robbery case the victim, a bartender, testifies that the defendant had
come into the tavern earlier in the night for a glass of beer. Three unwashed
glasses were found at the scene and were processed for latent prints. Two
of the glasses yielded prints, but these were of persons unknown, not the
defendant. The prosecutor suggests that the print examiner testify that the
third beer glass must have been used and then wiped clean by the defendant,
because the other two glasses were obviously not his. The print examiner
suggests that the prosecutor look elsewhere for this kind of testimony. The
prosecutor looks surprised.

Manipulation of Raw Data

An accident reconstruction expert with a computer is hired by a plaintiff’s
attorney to determine the speed of the defendant’s vehicle in a two-car
collision. The expert enters into his computer program the road surface drag
factor, skid and yaw mark lengths, and the location and severity values of
the vehicle damage. The first run of his computer program produces an
unrealistically high speed for the defendant’s striking vehicle. The expert
changes his drag factor estimate and tries again. The figures are still
outrageous. Three program runs and several crush data changes later, the
speed determination begins to look more believable. The defendant’s attorney
begins his attack with a subpoena for all five of the expert’s computer


As in the television game show where contestants reply in the form of a question,
certain managers give their subordinates a desired answer and demand that
they come up with the appropriate research questions to support it. During
one police department’s trial period of a 9mm pistol, a police officer wounds
an assault suspect. Because the suspect was not instantly incapacitated,
the police chief scraps the entire 9mm changeover program. He hears of the
FBI’s 10mm pistol program. One of the theories he returns with states that,
by virtue of its “larger size,” the 10mm is much better at striking blood
vessels than the smaller 9mm bullet. The department’s shooting instructor
points out that an extra half-millimeter along on each side of the 10mm bullet’s
diameter would not really make much difference, unless you missed a blood
vessel by half a millimeter with a 9mm bullet. Then the instructor begins
his litany about the training budget, that training is at least as important
as hardware, but the administrator doesn’t hear him, because it’s time to
play Double Jeopardy with the police chief.

Comparing Apples and Orangutans

In a product liability suit, the plaintiff’s attorney finds an expert witness
who will testify that, if the shotgun involved in the shooting had as safe
a firing mechanism as a rivet gun, the incident may not have happened at

Manipulation of Test Results

During a burglary trial, the prosecution produces seven latent prints recovered
from inside the victim’s house. The fingerprint examiner testifies that he
has identified these prints as belonging to the defendant. The prosecutor
suggests that the fingerprints are like seven little photographs of the burglar
inside the house. Because he does not want a repeat of an earlier case lost
to the defense attorney, the prosecutor calls a second examiner to the stand
to verify the comparison performed by the first. The prosecutor then states
that the seven latent prints, times two print examiners, make for fourteen
little photographs of the defendant inside the crime scene. Later, when jokingly
asked why he didn’t call a third examiner to up the score to twenty-one
fingerprints, the prosecutor replies that he had simply neglected to subpoena
another print examiner.

Compulsive Computing

A .223 Remington bullet is found lodged in a house several hundred feet to
the rear of a rifle practice range at which .223 weapons are frequently fired.
The investigators want to know if it is possible for a .223 bullet to fly
the several hundred feet necessary to reach the house, so they ask a firearms
examiner. The examiner, who had recently invested in a ballistics program
for his home computer, took down the range, wind speed, bullet shape,
temperature, barometric pressure, and several other pieces of data. His computer
charted the results. Finally, his answer to the investigators was, “Yes,
it’s possible.” As a qualified firearms examiner, he had already known that
the house was well within the range of the .223 cartridge and could have
given the same answer when first asked the question . . . without computation.


In many major criminal investigations it is the practice of a detective unit
to offer polygraph examinations to the suspects and, in cases of questionable
accusations, to the victims. While they are not admissible in court, the
polygraph results are relied upon as a valid investigative tool. One day
a young police officer shoots and wounds a juvenile who he claims fired at
him first, although no weapon is found. The officer claims he was also struck
several times about the head and shoulders with a board prior to the shooting,
although he exhibits no bruises, head injuries, or defense injuries to his
hands or arms. When asked about this lack of consistent injuries, a detective
reports that the young officer was wearing a bullet-resistant vest. The
detectives do not offer the suspect or the officer a polygraph examination
in this particular case.