ADA Maroun says they determined the bullets from the victim were fired from the defendant's gun with 100% accuracy. However no ballistics test is ever that accurate, and in real life it is far less accurate than depicted. When a bullet hits a hard target, like a person, it is often too deformed (especially if it hits bone or metal) to make a conclusive comparison. It is actually uncommon for a ballistics expert to say they can conclusively match a bullet to a specific gun, most of the time the best they can do is to conclusively say the bullet was fired from the same make, model and caliber as the gun in question.