you lie. >> traci williamson was an admitted liar and untruthful. >> reporter: and as for crystal's friend, jana, who said she saw c-styles and derek smyer together? the defense says derek was with a high school friend, and derek's sister danielle says the idea that derek met a gang-banger on the basketball court is absurd. but he grew up playing basketball and a bunch of other sports. didn't he play basketball in high school? >> he did play basketball in high school. he played basketball up into his junior year. i played basketball up into my sophomore year. never touched a basketball since. derek doesn't play basketball anymore. >> reporter: in this court, everything was on the line. that's when derek smyer, who'd never shied away from explaining himself in the past, took the stand. >>> coming up -- >> derek smyer. a dutiful dad to be? >> i was prepared to take care of my responsibility. >> when "dateline" continues. >>> it is a calculated risk for a defendant to testify at a trial. derek smyer was willing to take it. prosecutors had painted him a