ALBANY – The state Court of Appeals found yesterday that expert testimony on child sexual abuse was useful to jurors in one case but in another it was prejudicial to the defendant because of improper questioning by the prosecution.

Writing for the 6-0 court in each case, People v. Diaz, 52, and People v. Williams, 53, Judge Eugene Pigott Jr. (See Profile) said expert testimony on rape trauma syndrome, abused child syndrome or similar conditions is admissible if it can "clarify an issue calling for professional or technical knowledge, possessed by the expert and beyond the ken of the typical juror," quoting Delong v. Erie County, 60 NY2d 296 (1983).

Pigott held that the expert testimony in Diaz about "grooming" and other ways abusers seek to gain the confidence of young people they want to victimize was "permissible as helpful" to jurors in their understanding of the victim’s behavior. The testimony, for example, helped explain why the victim in Diaz did not immediately report the abuse, the court said.

"Although some of the testimony discussed behavior similar to that alleged by the complainant in this case, the expert spoke of such behavior in general terms," Pigott wrote in Diaz. "In addition, the jury heard the expert testify that she was not aware of the facts of the particular case, did not speak with the complainant and was not rendering an opinion as to whether sexual abuse took place."

Nonetheless, the Court of Appeals held that Randolfo Diaz should get a new trial because Acting Supreme Court Justice Debra Silber (See Profile) in Brooklyn refused to allow jurors to hear testimony that the victim had previously accused another man of sexual abuse.

Such testimony would have helped the defense "suggest a pattern casting substantial doubt on the validity of the charges," the court found, quoting People v. Mandel, 48 NY2d 952 (1979), and potentially aided the defense’s contentions that the victim frequently lied and that her charges of sexual abuse could not be believed.

The court took a different view of the expert testimony in Williams.

The judges said the testimony on child sexual abuse accommodation syndrome [CSAAS] turned prejudicial to defendant Bill Williams when Acting Supreme Court Justice John Ingram in Brooklyn allowed the prosecutor to pose hypothetical questions the court said came too close to the actual circumstances of the case before the court.

For instance, the prosecutor asked whether it was consistent with CSAAS for a "child living in her own home with a man who is her mother’s live-in boyfriend" and has the child straddle him, "that this child would not call out to another child similar in age who is sleeping in the very next room?"

Such a question drew a impermissible and prejudicial parallel between the syndrome the expert was testifying about in general and the particular circumstances of Williams, the court said.

"Such testimony went beyond explaining victim behavior that might be beyond the ken of a jury, and had the prejudicial effect of implying that the expert found the testimony of this particular complainant to be credible—even though the witness began his testimony claiming no knowledge of the case before the court," Pigott wrote.

In finding the potentially prejudicial error in Williams, however, the court declined to order a reversal and a new trial, ruling instead that the prejudicial effect of the questioning was harmless due to the "overwhelming" evidence of Williams’ guilt.

Williams is serving 46 years to life for first-degree rape and other charges involving two 12-year-old girls.

Diaz was sentenced to five years in prison for child endangerment and for engaging in a course of sexual conduct against a child.

Assistant District Attorney Ruth Ross in Brooklyn argued on behalf of the prosecution in both cases.

Anna Pervukhin represented Diaz and Kendra Hutchinson argued for Williams. Both lawyers work for Appellate Advocates.

In Diaz, Judge Jenny Rivera contributed her first signed opinion since joining the court on Feb. 11. She concurred with the retrial result, but disagreed with the other judges on the expert testimony. She said the testimony was prejudicial and its presentation to jurors warranted reversal of Diaz’s conviction.

"By referencing as abuser conduct the use of pornography, and the escalation in physical intimacy and sexual touching, the expert described conduct supporting the complainant’s testimony of abuse," Rivera wrote.

In other decisions yesterday, the court:

• Without comment, upheld a determination by the First Department in Kasowitz, Benson, Torres & Friedman v. Duane Reade, 119.

The lower court had determined that the law firm’s arrangement for representing Duane Reade in a dispute over ATM suppliers provided for a flat $1 million fee to the firm and no "success fee" above that amount, as claimed by Kasowitz, Benson (NYLJ, Aug. 8, 2012).

Judges Jonathan Lippman (See Profile), Victoria Graffeo (See Profile), Susan Phillips Read (See Profile), Robert Smith (See Profile), Pigott and Rivera concurred.

• Found that an attorney who practically "invited" jurors to convict his client of first-degree assault provided ineffective assistance of counsel and ordered a new trial for defendant Akieme Nesbitt in People v. Nesbitt, 28.

The court concluded that Nesbitt’s attorney was "mistaken" in his apparent belief that he had no good defense against the assault charge, though the jury did acquit Nesbitt of attempted murder. The attorney could have plausibly argued that the victim did not suffer the permanent or disfiguring injuries to justify the assault charge, the court said.

Assistant Manhattan District Attorney Patricia Curren represented the prosecution. David Klem of the Center for Appellate Litigation argued for Nesbitt.

The court decided the case in an unsigned memorandum by a 5-0 margin. The decision reversed a determination by the Appellate Division, First Department (NYLJ, Nov. 8, 2011).

• Unanimously upheld the child pornography conviction of a man who claimed that a search warrant for his video equipment, issued in May 2009, was invalid when police conducted a new search in January 2010 which revealed hundreds of previously overlooked illegal images (NYLJ, Nov. 22, 2011).

Convicted of an offense that carried six months in jail in 2009, Stephen DeProspero was prosecuted and convicted a second time in 2010 and sentenced to 18 years in prison.

Lippman wrote for the court in People v. DeProspero, 44, that the defendant had no "legitimate expectation" that materials found on the electronics, especially as they remained in the custody of authorities since their seizure in May 2009, would be private.

Citing CPL 690.55[2], Lippman wrote that "it is manifest that the continued validity of a search warrant and any assumption of custody it authorizes is not necessarily tied to the pendency of any particular prosecution. The duration of a warrant’s authority is more appropriately measured by the persistence of the cause for its issue."

Oneida County District Attorney Scott McNamara appeared for the prosecution. Frank Policelli of Utica argued for DeProspero.