The importance of this investigation, and the thoroughness and care with which it is conducted, cannot be overemphasized. Over the years, two key points have become clear. Second, even if lawyers had the skills, it is more cost-effective to employ those with recognized expertise in developing mitigation evidence. They are generally hired to coordinate an investigation of the defendant's life history, identify issues requiring evaluation by psychologists, psychiatrists or other medical professionals, and assist attorneys in locating experts and providing documentary materials for them to review. Although most often they assist counsel in assembling and interpreting the information needed in the penalty phase of a capital case, in some cases mitigation specialists are also called to testify about their findings.
Expertise is required at both ends.
Gathering and processing life-history information is a highly specialized art, and testifying effectively requires a separate skill beyond the professional discipline on which the testimony will be based. They are part of a cyclical process. Their assignment is open-ended. Testifying experts address particular referral questions. Mitigating evidence, on the other hand, deals with broad stretches of history.