a gas form. and i do that by heating the sample up. the gas is then collected or absorbed into the charcoal strip. >> they analyzed the samples and compared them to a database of over 750 known reference samples. >> it is like a doctor looking at an ekg. i have to be able to visually recognize what it is that i'm looking at. the sample that was removed from threshold was positive for gasoline. >> now investigators wanted to know who was the last person inside ann's home on the day of the fire. interestingly, neighbors saw michael bryant's truck at ann's home around 3 p.m., but the truck was gone by 5:00 p.m. the fire didn't start until two hours later. >> michael bryant and his wife were at the restaurant where he went, and the movie theater was in evans, which is a suburb of augusta, another good 15, 20 minutes to get there.