Death By IQ Score

Many states in the United States have created laws banning the sentencing of the death penalty to people with mental retardation.  What do you think happens when the life or death of a person hinges on a few IQ points?  In some capital cases, this is the case.  A person is considered mentally retarded if his or her IQ is below 70, but what does the court do if a person with an IQ a few points above 70 is involved in a capital crime?  In their article, Looking to Science Rather Than Convention in Adjusting IQ Scores When Death Is at Issue, Mark Cunningham and Marc Tasse wrote about how important finding the best way to interpret the standardized IQ score of someone a few IQ points away from a diagnoses of mental retardation in capital cases is.  

Most of us probably think that IQ scores are reliable, but what we might not know of is the Flynn effect.  You might be asking yourself, ‘What is the Flynn effect and why is it so important when talking about IQ scores?’  Well, the Flynn effect is the rise of mean IQ scores since the introduction of standardized IQ tests in the 20^th century.  The year that a standardized IQ test is created, the test norms reflect the contemporaneous population and therefore, a person’s IQ is an accurate comparison of the population at that time.  Over the years, the test norms for that IQ test become obsolete, so the mean IQ score of the general public rises and a given IQ score is not an accurate comparison of the current population.  An IQ test is re-normed about every 15 to 20 years, but in the meantime, IQ scores will rise because the IQ test norms are becoming outdated.

You can probably see why the legal system should consider and discuss the Flynn effect in capital cases where mental retardation is an issue.  Now that we see the problem, how can we fix it?  Truth be told, there is no easy fix.  Some professionals still do not understand or even know of the Flynn effect and others do not even agree with it.  Until there is a general acceptance of adjusting IQ scores to compensate for the Flynn effect, the practice will not become a prevailing convention in the professional community.

Ideally, having constantly updated IQ tests would fix the problem of continually rising mean IQs due to outdated norms, but frequently updating the tests would be extremely costly and time consuming.  Also, updating the tests frequently would require those who give the tests to obtain new testing materials and adapt the scoring procedures every time the test changes.

Cunningham and Tasse finally suggest a procedure to follow in capital cases where life is dependant upon a person’s IQ score.  They think that, in capital mental retardation hearings, someone needs to report the defendant’s IQ score, describe the Flynn effect, and report the defendant’s corrected IQ score.  To correct an IQ score, one would have to find how many years had passed since the creation of that IQ test and then multiply the number of passed years and the annual inflation rate of that specific test.   This procedure will hopefully save the lives of those with mental retardation when they are involved in capital crimes.

~Paula Zatko

Cunningham, M. D., & Tassé, M. J. (2010). Looking to science rather than convention in adjusting IQ scores when death is at issue. Professional Psychology: Research and Practice, 41, 413-419.