admitted to an affair, but denied the killings, in an exclusive interview with diane sawyer. >> did you murder your wife? >> no, no. i did not. >> reporter: tonight, peterson's attorney maintaining his innocence and saying the judge denied his client's request to speak at the hearing. >> he wanted to make it clear that there is no way he could have possibly harmed lacy and connor. >> reporter: and david, scott peter zone is still trying to get his conviction overturned. his lawyer is asking for a new trial and they have a hearing for that in february. david? >> all right, kayna whitworth with us tonight, as well. kayna, thank you. meantime tonight, on capitol hill, the head of instagram grilled about its effects on children, particularly young girls. so, what's being done and how soon? rachel scott on the hill tonight. >> reporter: tonight, the head of instagram appearing before congress for the first time, defending the popular social media app from blistering bipartisan criticism that instagram is toxic for children, especially young girls.