driving range. and critical correspondence about what they said was the murder weapon. >> one particular text message was very important. he's test-firing the gun, and he texts her saying, "this gun is so darn loud. " >> this was part of the prosecutors'plan to put dolores's gun in maliek's hands. fbi firearms expert brett mills told jurors about the results of that serial number restoration test he did on the gun recovered from the river. >> i wound up pulling up all but one of the digits. it wound up matching the bill of sale for ms. delgado's purchase of the revolver. >> is that like a bingo moment for you, when you put this stuff to the test and it works? >> finding out that the number i restored was basically the exact same one that was on her bill of laden, that was awesome. >> and mills had something else to tell the jury. remember, he'd done a test firing like this one through the barrel of