Police find a man slumped in a chair, gunshot wound to the head and a gun in his hand. The question is, did he kill himself or was he murdered?

One way to find out is by studying the gunshot residues collected at the scene by police.

Gunshot residues are produced when a firearm is discharged and particles are expelled through the gun’s muzzle, ejection ports and other gaps in a firearm.

Residues also remain on the firearm and cartridge, as well as small particles on the face, hair, hands, clothing and on persons or surfaces near the firing point.

Therefore, detecting gunshot residues is vital to many shooting investigations.

Chemistry Centre (WA) Managing Director John Hosking said projectile and primer residues in firearms are inorganic and can be detected by scanning electron microscopy electron dispersive X-ray spectrometry.

“Gunshot residue detection relies on finding primer particles containing the elements lead, barium and antimony,” Dr Hosking said.

“Such particles are common in centerfire weapons and unique to gunshot residues.”

Many shooting incidents in WA involve the 0.22 calibre rimfire rifles or sawn off weapons.

However, much of the 0.22 ammunition sold in Australia contains no antimony and therefore lacks a unique signature.

“Detection of the element boron has been the focus of a recent project researching borosilicate glass used in ammunition as a frictionator," Dr Hosking said.

Boron detection has been made possible by using the newly installed X-ray detector on the scanning electron microscope and through the University of South Australia’s Secondary Ion Mass Spectrometer.

For further information, telephone the Chemistry Centre (WA) on 9222 3177.