melinek thought max's injuries indicated he'd been assaulted before he fell. what's more, she questioned whether the fall itself could have happened as the sheriff's department described it. measurements showed the railing was 32 inches high. 6-year-old max was only 45 inches tall. >> his center of gravity was too low. even on the razor scooter, his center of gravity's too low to go over that bannister. >> reporter: it all pointed to a chilling, alternate scenario. according to dr. melinek, someone assaulted max, and then he somehow went over the bannister. in other words, this was a homicide. >> i would much rather have them say, "you know what? this was an accident. and here's why." no mom wants to hear that her son was a victim of a homicide. >> reporter: and if someone killed max, dr. melinek's theory focused on one person. >> i think rebecca was somehow involved, but how much she was involved and to what degree, she took that to the grave. >> reporter: that alarming suspicion was only the beginning because it wasn't just dina who was investigating. rebecc