The name of the inspector who had handled the analysis of the gunshot residue test was De Luigi. He was wearing a jacket and tie like someone who isn’t used to wearing them and looked like a young boy who had just joined the police. He was actually forty-four, as I discovered when he gave his particulars.

“You work at the regional laboratory of the Police Forensics Department, is that correct?”

“Yes. I’ve been working there for ten years.”

“What does the gunshot residue test consist of? I ask you to explain given that the jurors probably have no idea.”

“Yes, of course. The test is carried out when there’s a suspicion that somebody has fired a shot.”

“Can you describe to us the operation from the start?”

“Swabs are applied to the suspect’s hands, arms, face, neck and hair to collect particles deriving from a shot, if there are any, though they may only be identified during the next stage, when the specimen is examined under a scanning electron microscope.”

“One moment, I’m sorry. The test is done only on hands, face, hair, arms and neck? Aren’t specimens also taken from the nostrils?”

“Yes, also from the nostrils, that’s correct.”

“And from the clothes?”192

“It depends. If they’re the clothes the individual was wearing … or rather, if they’re the clothes the individual is believed to have been wearing at the time of the offence for which they’re being investigated, yes.”

“How exactly do particles end up, not only on the hands and arms, but also on the face and hair and in the nostrils?”

“When a firearm is discharged, a kind of cloud is released which spreads in a radius that varies depending on the type and calibre of the weapon. This cloud of volatile material falls rather like talcum powder, and may also settle on the face and hair.”

“How many hours after the event is it sensible to do the test?”

“It isn’t possible to indicate an exact time. It depends on a number of factors. If the individual has washed themselves thoroughly, it’s quite unlikely we’d find anything even ten minutes after the shot. If they were wearing surgical gloves and removed them in the correct way, we definitely wouldn’t find anything on their hands. Alternatively, if someone doesn’t wash themselves and hasn’t taken any precautions to protect themselves from contamination, like overalls, hoods and gloves which they then removed, traces can be found as much as four hours later. If more time passes, it’s very difficult: these particles are very volatile and tend to disperse, even if no washing takes place.”

“I have a specific question. If someone has fired a shot, and a few minutes later they’re given the test and nothing is found on their hands, arms or face, it’s very likely, not to say certain, that they’ve washed themselves. Is that correct?”