New York Federal Criminal Practice Blog
September 11, 2008

Second Circuit, Reversing Sex Offense Conviction Due to Improper Jury Instruction, Supports Admission of Defendant's Social Science Expert at Retrial

The ambiguous and often tragic world of alleged and actual sex offenders – running the gamut from harmless experimentation and role-playing to sinister preying on defenseless victims – is brought into sharp relief in the Second Circuit’s decision in United States v. Joseph, 06-5911-cr, 2008 WL 4137900, (2d Cir. September 9, 2008), in which the defendant had been convicted at trial of soliciting sex with a minor over the Internet.  The Court reversed because of an erroneous jury charge, but most interesting in the decision are the Court’s comments on the trial court’s preclusion of the defense’s expert witness – a social scientist with a specialty in Internet sexual communication.

Jury Instruction

The Court reversed the conviction because of an improper jury instruction – the district judge erroneously instructed the trial jury that it could convict if it found that the defendant tried either to entice a minor to have sex with him or “made the possibility of a sexual act with him more appealing.”  Since the latter alternative amounted merely to cyber-sex, which is not in fact a crime, and because there was a substantial risk that the jury had convicted based on that invalid alternate ground, a reversal for a new trial was mandated.  The defendant’s efforts to make sex with him “more appealing” can be evidence of enticement but is not, on its own, a basis of conviction. 

Admission of Defense Social Science Expert

What is remarkable about the case are the Court’s comments on an evidentiary ruling made at the trial.  The defense at trial was that the defendant had no interest in having sex with a minor.  He had merely engaged in harmless role-playing and genuinely believed that the target of his conversations was an adult posing as a child – a belief that was in fact accurate, since his correspondents were initially a 55-year-old woman (who surfs the web seeking sexual predators and then reports her findings to the F.B.I.) and later an F.B.I. agent.  The defendant claimed that if in fact, upon meeting his correspondent, she turned out to be an actual minor, he would have given her lunch and explained to her that “he was way too old to be involved with her.” 

To support this defense, defense counsel sought to introduce the testimony of a social scientist from the Institute of Advanced Human Sexuality in San Francisco, who had written his Ph.D. thesis on sexual communication on the Internet, and would testify “about a distinct culture of the Internet in which one can become a ‘fantasy character’” and would also explain “the realities and motivations of online role-playing via chatrooms and email,” including a phenomenon known as “de-masking” other chat-room participants.  The trial court rejected the proffered testimony primarily on relevance grounds.

Urging the district court to “give a more thorough consideration” to the defendant’s motion to present this testimony at a retrial, the Court held that the witness’s “field of study and experience qualified him to offer relevant testimony.”  In particular, the Court noted with approval the expert’s research techniques, which included “a large number of interviews” as well as study of chat-room conversations.  The Court went on, citing several other circuits:

Social science “research, theories and opinions cannot have the exactness of hard science methodologies,” and “expert testimony need not be based on statistical analysis in order to be probative.” “[P]eer review, publication, potential error rate, etc .... are not applicable to this kind of testimony, whose reliability depends heavily on the knowledge and experience of the expert, rather than the methodology of theory behind it.” In such cases, the place to “quibble with [an expert’s] academic training” is “on cross-examination” and goes to his “testimony’s weight ... not its admissibility.”  (citations omitted.)

The Court explicitly rejected a challenge to the expert’s testimony on the grounds that it relied on hearsay, noting that “[s]ocial science experts commonly base their opinions on interviews.”


Social scientists do some of the most fascinating, cutting edge research on human behavior.  Their findings confirm, confound and challenge our most strongly-held beliefs about feelings, motivations and actions.  The Court’s imprimatur in Joseph of the expertise of social scientists and the validity of their research methods has significant implications not just for sex offense prosecutions – which involve aspects of human behavior that many view as alien and abhorrent – but all kinds of prosecutions where the defendant’s behavior may be viewed as aberrant but is not necessarily the product of a criminal mind.  

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