DECATUR COUNTY, TN (WMC) - A critical piece of evidence in the murder of a west Tennessee nursing student is now under the microscope.
New court documents reveal the revolver in the Holly Bobo case has been tested and determined to not work.
Prosecutors called the gun a "critical piece of evidence" in the murder case, but now defense attorneys for Zachary Adams are casting doubt on that assertion.
The gun is a .32 Smith and Wesson long revolver. Court documents show the gun was found with four rounds in it in Decatur County.
Photos show the revolver was extremely rusted, and Adams' attorneys said it was inoperable.
Defense attorneys want to know how long the gun was on the ground. They believe it may have been there since Bobo was murdered.
The gun was cleaned and tested and does not show any blood in the cartridge.
Defense attorneys said a gun held close to her head would show blood spatter and blowback.
They believe Bobo was shot with a much larger and more powerful gun.
Adams is one of three men charged with murder in the nursing student's death.
There are reports that defense attorneys expect to call a witness who can give an alibi for Adams. He is set to go on trial September 11.