IF you’ve seen on TV enough of Crime Scene Investigation (CSI) episodes or read forensic articles of criminology experts, you should know that these are “misconceptions” about the “paraffin test” on crime suspects:
 Presence of gunshot residue (GSR) is proof that a person actually discharged a firearm;
 Negative GSR result is proof that a person didn’t actually fire a gun.
Niño Rey Boniel, the Bohol provincial board member accused of killing his wife, Bien Unido Mayor Gisela Boniel, reportedly was found negative of “gunpowder burns.”
His lawyers gloated but police waved it aside, saying it didn’t “affect” their case against Niño Rey. Of course, it’s hurting the state’s case build-up, if only in the propaganda battle between his lawyers and the police. Coming as it did with the succession of news reports about the fruitless search for Gisela’s body, the Niño Rey camp appeared to have scored another victory.
But the region’s police chief, Director Noli Taliño is right. The negative result doesn’t prove that Niño Rey didn’t discharge a firearm.
CSI and the experts tell us that compounds from a bullet, by the high temperature and pressure, “cool themselves and condense into particles” as they are expelled by the gunshot. The particles fly out from the cylinder gap, ejector parts and end of the gun barrel. Then they land on nearby surfaces and objects, including the hands and clothes of the shooter.
CSI technicians touch unique adhesive stubs to the hands of the suspect to transfer the particles to the stubs. A SEM or scanning electronic microscope will then determine presence or absence of GSR.
Niño Rey’s test reportedly didn’t show particles. Good for him but experts say it still wouldn’t prove non-firing.
The experts say it could be due to:
-- inadequate quantity of the particles, making them non-detectable, or
-- the time lapse between the shooting and the collection of the particles, which Taliño cited as probable cause (beyond six-to-eight hours, experts say, is already hopeless), and
-- blood or other moisture that may “defeat” the adhesive on the collection stubs, preventing a transfer of particles to the stubs.
Another factor that makes GSR tests inconclusive and unreliable evidence is contamination or transfer. A suspect can get particles on himself and his clothing from people and objects that originally got them in places where guns are discharged.
What’s the point then of conducting a paraffin test if its result has little probative value in court? CSI Network says it can be a useful tool for the police investigator “to put pieces of the puzzle together.”
In the Boniel tragedy, the GSR result, like the failure to recover Gisela’s corpse, is useful p.r. material for lawyers of the accused.
It would boost the spirits of Niño Rey and his alleged cohorts. But it would also encourage the police to build a stronger case that wouldn’t need the body of the victim or the outcome of a paraffin test.