The Supreme Court heard that a single particle of gunshot residue was discovered on a pair of shoes seized as part of an investigation into a double murder.

Tarah Helsel, an expert from Pennsylvania-based RJ Lee Group, said she tested several swabs taken from the hands and upper body of Syhon Akinstall two days after a deadly 2021 shooting at the Robin Hood pub.

She explained that she was specifically looking for particles that contained lead, barium and antimony — three metals found in the primer of ammunition.

“The reaction that happens when a firearm is discharged causes these elements to combine together,” Ms Helsel said.

“When all three of them are together in a particle, there are very few other sources of that particle other than the discharge of a firearm.”

She said that swabs taken from Mr Akinstall’s hands and his left ear revealed several “two-component particles” containing two of the three elements.

Ms Helsel explained that such particles can come from a firearm or other sources such as brake pads or fireworks, but the particles she found were consistent with those formed in gunfire.

She said that she also tested two grey-and-white sneakers that were mailed to her as part of the investigation.

Ms Helsel told the court that the left shoe was found to contain three two-component particles along with a single three-component particle.

“These are the only ones that, when they are present, allow me to say gunshot residue is found on a sample,” she said.

Ms Helsel told the court that particles can be washed off or transferred between sources, but said that she took part in a study in Bermuda which found that such particles were rarely found on the island.

As part of the study, she said she tested samples taken from a variety of different public locations, including restaurant tables, ATMs and pay phones, along with the hands of 100 volunteers.

The tests revealed no three-component particles at all, but two-component particles were found on the hands of two of the 100 people tested.

Mr Akinstall, 22, has denied the murders of Ayinde Eve and Micah Davis, as well as the attempted murders of Troy Eve Burgess and Derrick Golding, a police sergeant.

He also denies four counts of the use of a firearm to commit an indictable offence, namely the alleged murders and alleged attempted murders.

He has been charged in connection with a shooting at the Robin Hood Pub and Restaurant in Pembroke on October 26, 2021.

As his trial continued in the Supreme Court yesterday, Detective Constable Malcom Dill said that he was among the officers who attended the Robin Hood Pub on the evening of the shooting.

However, he said, he did not enter the building.

He told the court that he spoke with people at the scene and assisted a forensic support officer setting up lights in the restaurant’s rear parking area.

Two days later, he said that he and his partner drove Mr Akinstall from his home to Hamilton Police Station after his arrest.

“Upon arrival, we were met by the custody sergeant as well as the jailer,” he said.

“They were dealing with another detainee. They said to put him in the bullpen until they were ready for us.”

Mr Dill told the court that later that evening he collected samples from Mr Akinstall’s hands, neck, ears and head for gunshot residue testing.

He said that, following written instructions that came with the testing swabs, he collected two samples, sealed them up and signed them.

Under cross-examination, he said he could not be sure whether the police vehicle he used to visit the Robin Hood on the night of the shooting was the same one used to transport the defendant and that he had not personally cleaned the vehicle.

He said that while detectives sometimes clean the police cars, that task is usually performed by constables.

Mr Dill also said that he could not recall whether he sanitised the desk in the room where he took the swabs from Mr Akinstall before taking the samples.

The trial continues.

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