Forensic evidence 2

By Dr. Ken Manges, PhD, Forensic Psychologist

Objective evidence is crucial in a case involving a personal injury claim.  Physicians use X-rays, CAT scans, and MRIs to provide objective data.  Psychologists use psychological tests.

In an injury case, it can be expected that the plaintiff will have a bias, a subjective opinion about their suffering.  A psychological test can be used to objectify this subjective view. All tests, however, are not created equally.  When a test is properly structured, its results will allow the psychologist to correctly and objectively interpret the plaintiff’s account.  Not unlike taking your car in for a diagnostic, the test results will show where the problem lies, and how the problem compares to similar complaints by others.

Unlike a clinical setting, where test results are used to develop a treatment plan, which can be changed and augmented over time; a forensic setting uses test results as evidence.  Because all psychological tests are not created equally, and are easily misinterpreted, it is important to understand what psychological tests can and cannot do, what they can and cannot be used for, and how the test’s reliability and validity affect test results.

The Importance of Tests in a Forensic Environment

We’ll start at the beginning.  A psychological test is an objective and standardized measure of sample behavior.  Its function is to measure an individual’s strengths and weaknesses, the differences between one person and another, or to measure the effect of an incident or accident on the same person over time.  Because it is impossible to observe a person all day, to illustrate all of the different scenarios one may experience daily, or to ask all of the pertinent questions, a carefully chosen sample of questions or behavior must be made.  These questions, or samples, are the cornerstones of the test.  The test must ask the right kinds of questions, or it will not measure what is being asked.  It must ask enough questions, or the score will be rendered meaningless.  The test author must ensure that the test has content, criterion, and discriminate validity.   Only if the test passes muster on validity can the psychologist interpret the findings.

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Based on the test results, an interpretation of how this individual will act in a ‘non-test’ situation can be proposed, and a prediction of future behavior can be asserted.  For example, if a person is given a test composed of 20 varied math problems (addition, subtraction, and multiplication), a prediction could be made as to the person’s general math competence, based upon their performance on the test.  If a psychologist wanted to offer an opinion about the test taker’s math skills beyond addition, subtraction, and multiplication, however, he would need a different test.

A common pitfall is to rely on test ‘titles’.  Tests in a forensic environment can have similar names, leading the uninitiated to believe that they measure similar behaviors.  For example, there are many tests that measure a school subject called ‘reading’.  Yet, one test measures whether a person can pronounce syllables, a very small aspect of reading.  A score on this ‘reading’ test could not properly assess actual reading performance.

Uniformity in procedure in the administration and scoring of tests is a critical consideration in using the results in a forensic setting.  Uniformity in procedure includes the specific, detailed directions for the administration of the test:

  • Specific scoring instructions
  • Specific time limits
  • Oral and/or written instructions
  • Directions for the interpretation of a test taker’s answers

Administering Tests for a Forensic Environment

Administration, scoring, and interpretation of scores are meant to limit any subjective judgment and potential error on the part of the test administrator.  In order to pass Daubert and other court-imposed scrutiny, a test must be based upon empirical procedures and be readily duplicated.  If the test cannot be reliably re-administered, it will not pass Daubert standards.  Any variation from this set of procedures may produce suspect results, allowing the courts, justifiably, to disregard the test altogether.

As a point of clarification, some test measures are not meant to be used in a forensic venue. While these tests may have clinical use, they are not intended for use in asserting causal relationships.   They may suggest contemporaneous relationships and interesting findings for discussion, but are irrelevant for the purposes of forensic examination.

Despite all of the uniformity procedures being followed, test results can still be flawed if there is an absence of the test’s validity or reliability.  Daubert standards require error rates and reproducibility of findings.  Validity and reliability will be the subject of a future newsletter.

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Dr. Kenneth Manges, is a Forensic Psychologist and vocational expert who offers consultation and comprehensive evaluations. His analyses have been recognized for their clarity and scientific rigor. He offers reasonably certain opinions about the psychological impact of physical injury or emotional trauma as they effect earning capacity and the impact of loss on future work and quality of life.  Well regarded in the litigation arena, he is a trusted and respected authority and offers evaluations that have been consistently upheld in both state and federal courts.