3.4:600 Improper Trial Tactics
Under ER 3.4(e), a lawyer may not "allude to any matter during trial that the lawyer does not reasonably believe is relevant or that will not be supported by admissible evidence, assert personal knowledge of facts in issue, except when testifying as a witness, or state a personal opinion as to the justness of a cause, the credibility of a witness, the culpability of a civil litigant or the guilt or innocence of an accused." Lawyers are thus prohibited from stating at trial a personal opinion regarding a witness's credibility. See State v. Duzan, 176 Ariz. 463, 862 P.2d 223 (1993). Moreover, "[f]or ethical as well as legal reasons, an attorney should not imply to the jury that opposing counsel may not believe in the defense presented." State v. Hallman, 137 Ariz. 31, 37, 668 P.2d 874, 880 (1983) (citing State v. Travis, 26 Ariz. App. 24, 27, 545 P.2d 986, 989 (1976)).
Prosecutors have a special duty to see that defendants receive a fair trial. This duty, and some of its particular elements, are discussed in ER 3.8. See infra Section 3.8:100–3.8:1000; see also State v. Rodriguez, 192 Ariz. 58, 961 P.2d 1006 (1998) (noting that prosecutor neglected duty to disclose to defense matters related to the opinion of the state's fingerprint examiner). It is not misconduct, however, for a prosecutor to arrange a favorable plea agreement with one of several witnesses testifying against the defendant. State v. Dumaine, 162 Ariz. 392, 783 P.2d 1184 (1989). A prosecutor's suggestion, however, during the cross-examination of a mental-health expert, as well as during closing argument, that the defense expert had fabricated a conclusion of insanity, when there was no evidentiary support...
