The Texas Court of Criminal Appeals overturned the punishment phase of a capital murder trial because the district court excluded the testimony of a criminal justice professor who would have testified that the defendant's responsibility was lessened and that he was less of a future danger because an older woman groomed him for a sexual relationship for approximately five years before the crime. It found that Dr. Donna Vandiver qualified as an expert on female sex offenders, that her testimony would assist the jury in determining Christian Olsen's moral responsibility for the crime and the likelihood that he would be a danger in the future, and that her testimony would have a tendency to make the existence of any fact that is of consequence to the determination of the action more probable or less probable than it would be without the evidence. The erroneous exclusion of constitutionally relevant mitigating evidence offered by a defendant facing a possible death sentence requires reversal unless beyond a reasonable doubt it did not contribute to the punishment.
The district court thought that the opinion to be offered was psychological, and Vandiver admitted that she wasn't a psychologist. Vandiver's testimony was the best evidence that the defense had that Olsen shouldn't get a lethal injection.
I understand that one of Olsen's lawyers was Billy Carter. The error in the case seemed particularly well preserved.
Michael E. Keasler wrote the opinion for the CCA. Presiding Judge Sharon Keller concurred, explaining why she thought that this exclusion-of-evidence issue, normally not error of constitutional magnitude, was such in this case. Judge Lawrence E. Meyers dissented without opinion.
In short, it's easier to get a mitigation expert into a capital trial than it is other kinds of experts in other cases.
Thanks to CCA staffer Michael Falkenberg for correcting an error in an earlier edition of this post.