phone and his own personal phone with him, the night of the murder. and the next day, when he was driving his train. >> they moved north and then back south, on the railroad. >> but now, prosecutors had to tackle the head-scratching question of motive. why would tony kill melissa in the first place? debra villegas testified that tony became very jealous and angry with melissa, because she had virtually replaced him in the household. >> was melissa helping you through this difficult time in your life enough for this divorce? >> yes, ma'am. >> and that was the theory, in order to get deborah, he killed her best friend. >> you have these domestic homicides all the time, but this had a twist to it, because he did not kill deborah. >> then tony endeavors 23 year old son, caleb, was called to testify against his father. the usual blank stare on tony's courtroom face changed, as his son recalled how his father