Saturday Nashville police found the bodies of former Tennessee Titan star quarterback, Steve McNair and his girlfriend, Sahel Kazemi, dead in her condo. McNair was found on a couch. He was shot four times. Kazemi was shot once in the head. A semiautomatic pistol was found underneath her body.

McNair’s death has been ruled a homicide. A homicide is any killing of a human being by another human being. With four bullets in his body, two of which were in his head and the other two in his chest it is unlikely that he killed himself and homicide is a pretty good bet.

As to Kazemi the issue is a little more complicated. At first blush it looks like she killed him and then shot herself. And this is probably what happened. But the Nashville police are being somewhat cautious and rightly so by looking at other possibilities. For example it is certainly within the realm of possibility that a third party killed both of them and left the gun there in order to make it look like Kazemi killed McNair and committed suicide. After all, his wife, if she knew about Kazemi, might have a pretty good motive.

Last night Nashville police announced that Kazemi purchased the gun from a private individual Thursday evening. But prior to making any conclusions the Police Department asked the Bureau of Alcohol, Tobacco Firearms, and Explosives to run ballistics tests.

The Nashville police will now use their crime scene investigation unit to either confirm or deny the murder/suicide thesis. They will do a gunshot residue test on Kazemi’s hands to find out if she held the gun when it went off. It will be relatively easy since she is dead. If she was living she could have washed her hands or wiped them off.

Then they will do various ballistics tests. As a bullet travels through the gun’s barrel it obtains markings from the “lands and grooves” which are spiral lines inside the barrel created during manufacture to improve accuracy. As the bullet travels down the barrel it becomes heated and the “lands and grooves” become implanted on the bullet. Once on the bullet they are known as rifling marks. In addition, inside the barrel there are microscopic imperfections known as striations which create unique markings on the bullets and casings. Using special microscopes police experts can not only compare the bullets to the barrel but they can shoot bullets from the gun and determine whether they have identical markings to the bullets used to kill McNair and Kazemi.

Furthermore the gun can be examined for DNA. DNA on the gun will then be compared to Kazemi’s DNA and the police will be able to determine whether or not she held the gun.

By the time these tests are done the police will have pretty good evidence whether it was a murder/suicide or whether a third party killed one or both of the people.