both crimes. >> we were able to identify one suspect in the case and he's our prime suspect, matthew mullerer has never been charged in either case. we wanted to hear from muller himself. his attorney did not want muller to do an interview. however, muller agreed to see a visitor. "dateline" associate producer kayla ward spent 30 minutes talking with muller in jail through glass on the phone. no cameras, no recordings, no note taking allowed. >> what's your initial impression of him. >> extremely talkative. he was laughing and joking. talking about the book he was reading. >> what's his answer as to whether or not he's guilty of the crimes he's accused of? >> he wouldn't deny anything, but he wouldn't say he was guilty of anything. >> she asked him about samantha. >> i said we recently interviewed a woman and her case matches the other cases. he opened his eyes really wide. he couldn't believe that i was bringing this up. >> but he denied knowing anything about samantha's case or the one in palo alto. then kayla asked about denise huskins. >> he looked at me intensely and said can you imagi