D.H. Garrison, Jr.
Forensic Services Unit
Grand Rapids Police Department
Grand Rapids, Michigan
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 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 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 doesn’t go away unless you put your foot down and say … “Enough is enough.” 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 to see the 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, and 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 ant’s legs off, it becomes deaf!
You may recognize some of the scenes from the following examples of Bad Science at Work. Some are laughable, others disturbing. If you have not yet encountered 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 methods. When they ask for Bad Science, you can pity them as helpless people doing the right thing for the wrong reason. This kind of advocate needs to be taught … and watched.
Misinterpretation of Test Results
In a robbery trial, 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, seized, and later processed for fingerprints. Two of the glasses yielded prints, but they belonged to persons unknown – not the defendant. The prosecutor suggests that the fingerprint 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 used by him. The fingerprint 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 striking vehicle. The expert changes his drag factor estimates 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 of the tests with a subpoena for all five of the expert’s computer printouts.
Comparing Apples and Orangutans
In a product liability suit, the plaintiff’s attorney finds an expert 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 all.
Manipulation of Test Results
During a burglary trial, the prosecution produces seven latent fingerprints which were recovered from inside the victim’s house. The fingerprint examiner testifies that he has identified these prints as belonging to the defendant. The prosecutor testifies that the fingerprints are like seven different photographs of the suspect 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 comparisons made by the first. The prosecutor then states that the seven fingerprints, times two examiners, make fourteen little photographs of the suspect inside the house. Later, when 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 a third examiner.
A .223 Remington bullet is found lodged in the side of a house several hundred feet to the rear of a rifle practice range where .223 ammunition is frequently used. The investigators want to know if a it is possible for a .223 bullet to fly the several hundred feet necessary to reach the house from the range, 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 investigator was, “Yes, it is possible.” As a qualified firearms examiner, he had already known that the house was well within the range of the .223 bullet and could have given the same answer when first asked the question…without computation.
In many major criminal investigations, it is the practice of detectives to offer a polygraph examination to the suspect, and, in cases of questionable accusations, to the victims. While they are not admissible in court, the polygraph results are relied upon as a valuable investigative tool. One day a young police officer shoots and wounds a juvenile who he claims fired upon him first, although no weapon was 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 officer was wearing a bullet resistant vest. The detectives do not offer the suspect or the police officer a polygraph examination in this particular case.
No Scientific Methodology
A city truck driver runs a stop sign and causes an accident which results in severe injuries. Instead of relying on skid marks, crush damage, and scene evidence, the city authorities order a traffic investigator to conduct acceleration tests to determine the maximum possible speed the truck could have achieved in the one-block distance leading up to the crash. Because the truck was disabled in the crash, the traffic investigator uses a motorcycle to run the one-block acceleration test and reports back a peak speed of 35 miles per hour for the city truck.
Too Many Cooks Spoil the Broth
A city bus rear-ends a carload of teenagers, killing four. The first traffic investigators at the scene measure the skid marks of the bus and determine that the bus driver was speeding. A national civil rights leader claims that the bus driver is being made a scapegoat by the city solely because he is of a racial minority. The follow-up investigation by the city authorities reports that the original traffic investigators, who have been abruptly removed from the case, must have been measuring tire marks tracked through melted roadway tar and that, on second thought, the city bus driver was not speeding. A local television station gets a radar gun and reports that most drivers, including city bus drivers, regularly exceed the speed limit on this stretch of road. Tire tracks in tar look nothing like skid marks to the trained eye of the investigator. Excessive speed aside, it is unlawful to follow another vehicle at an unsafe distance.
Pursuit of the Inconsequential
In the faked robbery of a fast food restaurant, the night manager shoots to death an employee in a walk in cooler, hides the “stolen” money and a .357 magnum revolver and calls police. The crime scene personnel notice fallen dust on a restroom floor and discovers the money hidden in a ceiling panel. The revolver is found among the night manager’s possessions. In preparation for the trial, the prosecutor asks for a shooting sound test to be done inside the restaurant’s walk in cooler. This, he says, will determine whether or not the fatal shots could have been heard by a teenage girl who was having sex with a man (not her boyfriend) in her boyfriend’s van parked across the street from the restaurant. The girl, who incidentally had a full length cast on her leg at the time (another mystery altogether), did not recall hearing much of anything, least of all gunfire. Her partner that night also somehow missed the sounds. The crime scene investigator refused to participate in such an experiment, arguing that it was irrelevant, invalid, and just plain silly…and what would it prove, anyway? The prosecutor suggests that the defense might use the fact that the girl had not heard the shots to argue that the time of the murder was somehow different. “Then let the defense make a sound test,” the investigator says, leaving. The prosecutor is insistent. After being turned down by the police firearms instructor and the state regional laboratory examiners, the prosecutor gets three detectives to fire the shots for the sound test. To duplicate the sounds of a .357 magnum, they load the weapon with light .38 special target loads; they fire the quieter ammunition into a sandbagged pipe inside the walk in cooler so as not to make holes in the walls. It is several months later, and the air temperature is sixty degrees cooler than the night of the murder. By the time the test begins, the noisy morning rush hour traffic has clogged the street in front of the restaurant. To duplicate the hearing of the busy girl with the cast on her leg and other things on her mind, they use the prosecutors ears as he stands across the street. (Later there were several profane allegations about what the prosecutor had to endure to fully recreate the event.) The results of the test? “It sounded like a hand clap,” said one of the detectives stationed in the restaurant’s dining room. So, apparently one can induce deafness by making love to a girl in a full-length cast, the same as one can by cutting all six legs off an ant.
Examples of truly Bad Science are everywhere. So, what can one do to avoid being ambushed by the Bad Scientists? Three philosophical exercises come to mind. The first is the methodological battle plan called “Ockham’s Razor,” named after the 14th century philosopher William of Ockham. In philosophy, a problem should be stated in its basic and simplest terms. In science, the theory that fits the facts of a problem with the fewest number of assumptions is the one that should be selected. This is the great-grandfather of K.I.S.S. (Keep It Simple, Stupid) theory, and it works well against Bad Scientists.
The second tactic is termed “reducio ad absurdum,” which is the disproof of a proposition (or stupid experiment) by showing the absurdity to which it leads when carried out. A good example of such a situation is the aforementioned case of the prosecutor who argued that seven fingerprints identified by two fingerprint examiners make a total of fourteen little traces of the burglary defendant. The reduction ad absurdum of that case is the notion that a third fingerprint examiner would up the ante to twenty-one clues, or that a dozen examiners identifying a single print would make for twelve traces of the defendant. The clues multiply like bunny rabbits. The mind boggles. Think of where the Bad Scientist is trying to lead you. And look to the dark at the end of the tunnel.
The final fallback is to common sense, the bane of Bad Scientists the world over. It was Thomas Huxley who said, “Science is simply common sense at it’s best – that is rigidly accurate in observation, and merciless to fallacy in logic.” This is where the juries trod on the best laid plans of eloquent attorneys. They step back for a moment and resort to instinct, to common sense. Lawyers, especially those true believers who do the prosecuting, are notoriously bad at feigning common sense. They are better at reduction ad absurdum. Cops, on the other hand, are excellent at instinct and common sense, but poor at seeing the absurdity of a proposition’s logical conclusion.
One needs to stand one’s ground. And this means more than just Do Not Testify To Methods Beyond Your Expertise, or Do Not Selectively Ignore Evidence To The Contrary, or Do Not Overstate Your Qualifications. Standing your ground means you have to get in the face of anyone who even hints at being a Bad Scientist. You will need to gently redirect the novice Bad Scientist, showing him the light and where you stand. With the more seasoned advocates, (prosecution or defense), you may need a chainsaw to carve out your turf in the Bad Scientists office, be s/he a medical examiner, lawyer, or supervisor. Draw the line. Let them know that enough is enough. J. Robert Oppenheimer said it best when he wrote: “The scientist is free, and must be free to ask any question, to doubt any assertion, to seek any evidence, to correct any errors.”