It’s Not the Excuse, It’s the Expert

James Q. Wilson is professor of management and public policy at UCLA. This is adapted from his new book, "Moral Judgment" (Basic Books)

As some critics say, we do have two kinds of trials, one for the rich and another for the poor. But the difference lies not, as critics claim, in the penalties defendants suffer but in the strategies they employ. The celebrated defendant takes a chance: jury acquittal versus a tough penalty. The average defendant negotiates a deal: almost certain conviction and a modest penalty.

The celebrated defendant--one who is either wealthy or notorious--can take on a lengthy trial in which expert witnesses play a large role. With the possible exception of those facing the death penalty, the law does not give equal access to such witnesses for all defendants. Only defendants who can afford them enjoy them.

But what do they enjoy? Not, I think, real science, but often pretend science. Real science involves testing theories by repeated and independent experiments that, if they never refute the theory, lead one to accept (provisionally) the theory as stated. Real science has been used to establish that, so far as we can tell, every person has a unique set of fingerprints and a distinctive DNA profile. And science has been used to show that polygraphs--lie detectors--do not always detect lies and that voice prints do not always identify the speaker.

The science that seeks to explain human behavior--the science that is practiced by psychologists and psychiatrists--is much less robust. At best, it is often little more than an assertion that in a certain percentage of cases a person with certain traits (such as a score on the Minnesota Multiphasic Personality Inventory) is likely to be part of a group that will be more likely to behave in a certain way.


At worst, it is often much less than this. Someone will notice a social problem, such as battered women, abused children or intoxicated men. That person will interview people who have been battered or abused or drunk and will describe their characteristics. The description often is written by advocates--people who care deeply about battering or abuse--and frequently will not reflect a careful effort to show in what ways (and with what frequency) women who have and have not been battered or children who have and have not been abused differ. And even if they are written by earnest scientists, such descriptions rarely can say that a particular battered woman, abused child or drunk man will behave in a particular circumstance in some distinctive way.

But expert witnesses are allowed to give their opinions on these matters in court after only the most cursory effort to establish their standing and objectivity as scientists. In many cases a person can become an “expert” and thus be entitled to offer opinions and not simply recount observations because he or she is “qualified” by “knowledge, skill, experience, training or education.” In short, people with PhD degrees or some training that approximates that are experts whether they have any scientific knowledge or not.

Some states, including California, have used a rougher test, the Frye rule, under which testimony must survive a test of general acceptance in its field. That is a useful restriction, but courts frequently make exceptions to it. In 1989, the California Supreme Court decided to allow a psychologist to testify that a woman charged with sexual perversion against children had a “normal personality” and had been “falsely charged” because he had given her the MMPI and another written test.

In 1993, the U.S. Supreme Court tried to set tougher standards by urging courts to use a more scientific standard for judging would-be experts: Has the statement they wish to submit withstood serious efforts to falsify it in reputable, peer-reviewed journals? But just how this new test was to be applied was left to the usual lawyer-dominated process--"vigorous cross-examination,” which of course leads to the threat of appeals to a higher court.


Criminal trials that produce appeals have increased dramatically in recent decades. Anyone with a grasp of how organizations behave should be able to guess what this means. To avoid successful appeals, judges allow defendants to admit as much evidence as possible, including expert witnesses. Courts in many states have been instructed to allow women who kill their husbands or lovers to use the “battered women’s syndrome” as a mitigation or excuse. A large and tragic number of women has been battered; supplying help to these women is a matter of great importance. But converting the fact of being battered into a “syndrome” that can explain why a battered woman must kill her sleeping husband is suspect. This syndrome has in fact no explanatory power, in part because no one has explained who is and who is not affected by it or why it adds anything to our conventional theories of self-defense.

Matters are much the same with child abuse or intoxication. There are, alas, many abused children; there are even more people who drink too much. But why should these facts, taken alone, provide a way of mitigating a penalty when the many other causes of crime do not?

The effect of expert witnesses on juries can be profound. Many experiments have tested how jurors react to different versions of a mock trial. The versions differ in how much information is given about the legally irrelevant but socially important features of a defendant. Suppose a woman kills her husband. What is legally relevant is whether she acted in self-defense, under duress or in the grip of insanity so great that she was hallucinating. What is not relevant is whether she was a good mother or a bad one. But when jurors are told about her status as a mother, the penalties they will support change dramatically.

This helps explain an otherwise puzzling fact. Americans by and large are deeply upset about crime and quick to criticize judges and jurors who seem to give apparently guilty defendants an acquittal or a light sentence. But take 12 people more or less randomly from our society, put them on a jury and expose them to lengthy accounts of why the defendant acted as he or she did, and many of them--for example in the first Menendez brothers trial--will vote for the lightest penalty.

American criminal courts have not accepted a long list of abuse excuses. What they have accepted is a long list of “expert” claims about the plight of defendants who are rich or famous enough to enlist those witnesses. The task for our legislatures is not to purge false excuses from the criminal code but to place meaningful restrictions on who may be summoned as an expert and what they may testify about.