( CNN ) -- A forensic consultant for the defense of a former Kansas police officer accused of killing his wife testified on Thursday that evidence showing the man had gasoline on his pants could have been contaminated . Brett Seacat is on trial for the first-degree murder in the death of his wife , Vashti . Prosecutors say he shot his wife in April 2011 and set their home on fire , but the defense says Vashti was depressed and committed suicide after torching the house . Pants collected from Brett Seacat the morning of the incident were n't placed in the appropriate bag , according to Gene Gietzen , the forensic consultant . Investigators on the scene placed the pants in a paper bag and transferred them to a plastic bag about an hour later . Gietzen says an unlined paint can or a nylon bag is the appropriate transport method for any evidence that may contain an accelerant -- in this case , gasoline . Paper and plastic bags allow the accelerant to escape and can even let accelerant present in the air cross-contaminate evidence , according to Gietzen . Gietzen showed the court notes written by Chris Riddle , the forensic scientist from the Kansas Bureau of Investigations who worked on the case . Riddle appeared to have concerns about the packaging of the pants , writing , `` Not sealed properly for fire debris analysis ! '' Monte Weldon , a neighbor of the Seacats , also testified on Thursday that he was shocked to learn the couple was splitting up . He approached them in their driveway the day before the incident , wanting to know what he could bring to a barbecue that was originally scheduled for the day Vashti died . Before Weldon could even ask the question , he said , Brett Seacat told him the party was off because the couple was divorcing . Weldon said that Seacat did n't seem to be angry or enraged and that he was n't making any secret of the couple 's separation . Weldon also testified that Brett Seacat had plans to fix up the home , so he was surprised to hear that Seacat was being accused of burning it down . Weldon said he sold sand and dirt to Seacat to build a sandbox and to fill in a hole in his yard . Seacat was also planning to change out all of the light switches in the home , Weldon said . `` It was such a beautiful house , you could n't help but talk to him about it , '' said Weldon . `` He loved the house . '' Seacat has said he was sleeping downstairs on the night of the fire , HLN affiliate KWCH reported . He heard a noise , and moments later , his wife called him on his cell phone , saying he should get their two boys out of the house before they got hurt . He then purportedly heard two pops . Brett Seacat went upstairs and saw flames . He reportedly said he found his wife in their bedroom and tried to save her . Prosecutors say Brett Seacat 's story does n't make sense . For one , he had no soot or blood on him , they say , according to KWCH , and only a small burn on his foot . He and the couple 's sons escaped from the blaze unharmed . The Seacats ' home in Kingman , Kansas , sits not far from the courthouse where Brett Seacat is standing trial . Despite extensive fire damage , the house still stands ; a brick chimney pokes out of the charred remains . `` I 'm smart enough that if I wanted to kill my wife ... I could 've come up with something better than this , '' Seacat told investigators about the shooting and the fire . `` This is what a crazy person does . ''
Vashti of Kansas , Kingman , is accused of killing his wife , Brett Seacat , in the day . At trial , a forensic scientist for the defense questioned the handling of evidence . A neighbor testified that he was surprised that the couple was divorcing .