Experts

Experts

It is often useful, sometimes even necessary, to call experts as witnesses for the defense. In computer crime cases, the defense may use expert testimony to discredit or repudiate the testimony of the prosecution's investigators, criminologists, auditors, or computer experts. If experts are used for this purpose, counsel should ensure, through discovery, that the witnesses have an opportunity, before trial, to examine the prosecution's evidence that is relevant to their testimony. Counsel should review the general content of each expert's testimony with the witness; in some instances, the expert may be questioned as to what kind of questions should be asked during trial to prove or disprove key allegations.

Defense counsel can use cross-examination of the prosecution's experts to discredit their testimony. It may be possible to elicit testimony from the prosecution's expert that no tests were done to see if the fingerprints of someone other than the defendant were found on a terminal at which the defendant was supposed to have committed the crime. Where a log is maintained of individuals who have access to the computer, it may be possible to elicit an admission that no effort was made to see if anyone could have overridden the logging mechanism, and in effect, kept their own guilt from being recorded in the log.

In the prosecution for interstate transportation of stolen property, arising out of a defendant's offering stolen computer equipment for sale, it was not error for the trial court to exclude defendant's proffered testimony of a psychiatrist that the defendant suffered from dependant personality disorder with narcissistic features, in order to buttress defendant's claim that she had impaired ability to know that computer equipment was stolen. Under the Federal Rules of Evidence, an expert is prohibited from expressing an opinion or inference as to whether defendant did or did not have the mental state or condition constituting an element of the crime charged or of defense thereto where the psychiatrist's testimony would have contained an implication regarding defendant's mental state, leaving it to jury merely to murmur "amen."FN60

Cumulative Supplement

Cases:

Community acceptance in pornograpy prosecution: Defendant in prosecution for promoting obscenity was not entitled to introduce testimony of expert regarding availability of allegedly comparable materials on the Internet, as mere availability of such materials did not show that community accepted such images, even if they could be viewed at public library, and defendant did not show reasonable resemblance between such materials and videotape that was subject of charged offense. Burden v. State, 55 S.W.3d 608 (Tex. Crim. App. 2001); West's Key Number Digest, Obscenity 16.