A witness reiterated on Thursday that although she found a trace of nitrate — a major component of gunpowder — on a swab purported to have been taken by one of three men killed by police on January 12, 2013 during an alleged shootout, she was unable to conclude that it was transferred during gunfire.

The witness — a retired lab analyst — while testifying on Wednesday in the murder trial of six policemen in the Home Circuit Court in Kingston, had told the seven-member jury that after testing swab samples taken from the hands of the three deceased and T-shirts belonging to two of them, she was not convinced there was enough evidence to definitively say that the nitrate came from gunpowder. She told the court that the trace of nitrate was found on the hand of only one of the deceased.

Nitrate, the witness said, is a component of the environment and can found in soil and could be transferred to a person if contact is made with it.

On Thursday, she repeated the explanation, but under cross examination from defence attorney Hugh Wildman she admitted that she was unable to tell the court what percentage of nitrate was found on the swab.

Wildman asked her if she found any trace of soil when testing the swab samples.

“I was not looking for soil,” the witness responded.

Wildman probed to find out what percentage of gunpowder is made up of nitrate compared to lead, antimony, and barium which are other main ingredients.

The witness explained that she was unable to give the percentage of nitrate in gunpowder. She also shared that she did checks to determine the presence of elements other than nitrate.

The witness also admitted that she did not know what quantity of gunpowder is made up of lead, barium or antimony.

She explained that lab tests can be done to ascertain the percentage of each of the elements, but admitted that she did not employ those procedures in this case, even though she was aware that the swabs were connected to a fatal shooting.

Wildman suggested to the witness that the existence of nitrate on a person is compelling evidence that the individual fired a gun.

“No Sir,” she responded, “even though it’s a common component in gunpowder residue. It is caused by the burning of nitrocellulose, which is burning during the firing process and as a result the gunshot residue would also have nitrates in it, considering the components. Depending on the proportion, finding nitrate alone would not be significant as finding the others. That is the basis of my conclusion, that it is not gunshot residue,” the witness said.

The witness further explained that nitrate picked up from soil is not different from nitrate found in gunpowder residue. She also said that she did not see the need to carry out a particular test to determine what type of nitrate was found on the T-shirt.

The witness accepted that it was possible for gunpowder residue to no longer be present where it was before, due to a number of factors.

She explained that delay before testing could be a factor, as well as the moving of a body to hospital and then to a morgue as well as the washing of the body.

Wildman asked the witness to say whether a rapid loss of gunpowder residue occurs between one and three hours after landing on a surface.

She responded that between three and six hours afterwards there is a rapid decline in presence of gunpowder residue.

Wildman raised the point that the hands and shirts of the deceased men were swabbed after 6:00 pm, many hours following the shooting. He pointed out that the shooting took place around midday and asked the witness if that could be considered a significant delay in taking samples.

“That time frame does fall within the three to six hours. There is the possibility of loss of gunshot residue,” the witness replied.

On trial for murder are Sergeant Simroy Mott, Corporal Donovan Fullerton, and constables Andrew Smith, Sheldon Richards, Orandy Rose, and Richard Lynch. Corporal Fullerton is also charged with making a false statement to the Independent Commission of Investigations.

The policemen are on trial in relation to the January 12, 2013 shooting deaths of Matthew Lee, Ucliffe Dyer, and Mark Allen. They were killed in an alleged shootout with the police. A fourth man was said to have escaped. Two firearms — a Mac 11 submachine gun and an Arcus 9mm pistol — were reportedly seized from the men following the incident.

The other attorneys representing the cops are John Jacobs and Althea Grant Coppin.

Trial judge, Justice Sonia Bertram-Linton is presiding over the case.

The trial continues today.