return home to make it look like he was home that night to make it look like he took a call from joseph mcstaythe evidence to prove that, yes. >> how strong is that proof? how reliable is the evidence gathered at the mcstay house weeks after investigators say they were murdered there? >> tons of critical evidence could have been lost in those first 15 days. >> 15 days in which people were in and out of the house. >> so many things in there that could have been relevant to the case. investigative journalist s steph watts. >> we don't know if somebody in that house was related to or had knowledge of the crime could have removed items that could have been significant to solving this case. could have removed items that could have indicted them in this case. >> i don't think that you can seal a home for that long unless you are actually investigating a murder, and at that time, it wasn't. >> we know that the family members went in and out and susan mcstay went in and cleaned the counters. she couldn't stand the house was dirty, she went in and threw out dirty diapers. and mike mcstay took the video