if you're such a hot shot expert -- >> right. and -- >> reporter: how does this error creep in? >> and he said, "well, it was a mistake." >> reporter: the same went for the dna evidence, attack the credibility of the analysis. the defense said the dna results, returned within a few days, were rushed through the police lab because of rothstein's connections. attorney fleisher also suggested there could have been cross contamination to tilt the scale so the results pointed at tony. >> our goal was to educate the jury on the rothstein connections, and the rothstein influence. >> reporter: had meddled with the physical evidence? contaminated it maybe? >> we can only speculate. but when a man is as powerful a guy as -- as rothstein was, people would think that they could do things. they could conjure up dna. >> reporter: and use it to frame tony villegas. before the defense rested, the judge asked tony villegas if he wanted to testify. >> is it your wish to testify or remain silent?