Gunshot Residue (GSR) Test


Collected on: December 25, 2002

Collected by:  Detective Brocchini

Reason:  The gun in the glove compartment of the Ford Pickup

Media Reports: 

Received by:  Administered on-site at the Modesto Police Department

Received on:  Not sent in for analysis, still remains in the MPD evidence room

Results: Establishes that Scott Peterson had only one wound on his hands that night, a single scrape on his right index middle knuckle


Initial Suspicion


After Brocchini quizzed Scott about the hand gun, he asked Scott if he would submit to a gunshot residue test on his hands.  He agreed, but asked if exhaust from an outboard motor would give a false reading. Brocchini said it wouldn't.


The Testimony


The Prosecution didn't mention the gunshot residue test, but Geragos reviewed it with Brocchini in his cross and reviewed the process for taking the test, which requires swabbing various areas of each hand. 


Detective Grogan confirmed that the residue test was never sent in for testing, but remains in the MPD evidence room, because "Scott said that he had been out on the water that day, that he got wet while he was out there. He said that he had taken a shower and changed clothes. And so the gunshot residue test is not something that stays with you through a shower. It needs to be done relatively soon to the time that you fire a weapon."  Grogan also confirmed that Brocchini did not observe any other cuts, scrapes, scratches or wounds on Scott's hand as he administered the gunshot residue test.




The only purpose for administering the gunshot residue test seems to be to give Brocchini an excuse for making a good visual examination of Scott's hands.  That the test served no other useful purpose is pretty clear.  That Scott had no evidence of a struggle, such as scratches or bruises, is also pretty clear.