State v. Thomas C. Burton, 2007 WI App 237
For Burton: Timothy A. Provis
Issue/Holding: Testimony by a “gang expert” as to the gang-affiliation of certain witnesses, in an effort to explain their motive to testify as they did, was irrelevant in the absence of any evidence that the defendant was himself a gang member:
¶14 Burton’s central argument on appeal is that Warmington’s testimony was squarely barred by State v. Long, 2002 WI App 114, 255 Wis. 2d 729, 647 N.W.2d 884. There, we stated that “[f]or a witness’s gang affiliation to be relevant to show bias in favor of [the defendant], the State was required to establish [the defendant]’s gang affiliation.” Id., ¶19. …
¶15 … The State argues that Bowens’ and Jones’ gang connections are relevant to show not, as in Long, their bias in favor of the defendant, but rather their “bias against the prosecution.” …
¶16 But the State’s focus only on Warmington’s identification of Bowens and Jones as gang members ignores the much broader reach of Warmington’s testimony.  Identifying witnesses as gang members may be admissible where there is a tight fit between their gang membership and some specific motivation to be untruthful, as is generally present in common-membership cases. See Abel, 469 U.S. at 47-48. But this is not what Warmington testified to; rather, he spoke in generalities about people “up in that area” not cooperating with the police out of fear of retaliation, or because “they in some way, shape, or form participated in something that led to them being shot.” Warmington went on to testify that “witnesses” (here it is unclear whether he is talking about gang members or neighborhood residents) will make “excited utterances” to the police that they later deny. 
¶17 We agree with Burton that this testimony, whether viewed as going to bias or character for truthfulness, was prejudicial because it invited the jury to discredit the several witnesses who testified favorably to Burton, either by tarring them with undemonstrated gang affiliation or simply based on the neighborhood in which they live. We see little, if any, probative value in this sort of testimony. …
¶18 We also find objectionable Warmington’s testimony that a gang member who had been “publicly embarrassed” would “feel the need to gain that respect back … through retaliation, through physical confrontation, a fight, a shooting.” Though Warmington did not mention Burton by name, the whole line of questions and answers is obviously intended as support for the prosecution theory that Burton shot Bowens in retaliation for the alleged robbery; indeed, the prosecution explicitly sought to introduce this testimony to show Burton’s motive. As Burton points out, the State adduced no evidence that he was in any gang ….
¶19 Given the low to nonexistent probative value and highly prejudicial nature of the portions of Warmington’s testimony we have discussed, we hold that the circuit court misused its discretion in admitting it. See Wis. Stat. § 904.03.
The court cites with approval, and therefore seemingly adopts (¶17), the concurrence in People v. Roberts, 65 Cal. Rptr. 2d 17, 22 (Ct. App. 1997) (warning of dangers of “generalized ‘bias’ testimony based on group tendencies”).