US v. Williams: Williams was tried and convicted of being a felon in possession of a firearm. At trial, two police officers testified that they approached Williams outside of a Baltimore apartment complex when they suspected him of selling bootleg CDs and DVDs. Williams was placed under arrest because he lacked a vendor's license and was searched. During the search, according to one officer, Williams was wearing a fanny pack around his waist. When the officer removed the pack, he noticed a bulge in Williams's waistband that contained a firearm.
At trial, Williams stipulated to his prior felony convictions and did not intend to testify. However, he wanted to demonstrate to the jury that the fanny pack seized by the police was too small to fit him. The Government objected, arguing that if such a demonstration took place, Williams would have to be subject to cross-examination. The district court agreed, holding that such a demonstration would be "testimony" and require Williams to waive his Fifth Amendment right to be silent. Williams eventually did testify about the encounter with police, denying he possessed a gun (it was left by a man who fled when police approached, as he was the real bootlegger), and put on the fanny pack (it was too small - just like OJ's glove). During cross examination, the Government elicited the nature of Williams's prior convictions, including one for illegally possessing a firearm.
On appeal, Williams argued that the district court erred by considering the demonstration to be the equivalent of testimony requiring cross-examination and the waiver of his Fifth Amendment rights. The Fourth Circuit agreed with this argument, noting that the purpose of cross examination is to probe the capability for recall, bias, etc. of a witness and that such considerations weren't applicable to demonstration evidence (although they would be relevant to the testimony of someone who said the demonstration resembled the real act). However, given the strength of the Government's case, the error was harmless. In addition, the negative evidence that came out during the cross-examination of Williams came not from questions about the demonstration, but from Williams's decision to testify about the encounter with police. Had he limited the scope of his testimony, cross-examination would have been similarly limited. Williams's conviction was affirmed.