A FIREARMS expert told the Rhys Jones trial that tests on the alleged weapon could not prove it was the gun used to kill the Liverpool schoolboy.

Doubt was cast yesterday on prosecution claims that a Smith and Wesson revolver recovered by police was used to fire the shots that fatally wounded the 11-year-old.

Liverpool Crown Court heard from forensic scientist Angela Shaw, an expert in firearm discharge residue (FDR).

She explained to the jury how gunshot residue can be transferred to a person and the factors that can make a difference.

There are three common types of FDR, she said. These make up 90% of the FDR they see in cases.

For this inquiry, Ms Shaw was asked to analyse various swabs and samples, including Rhys’s football shirt, glass shards from the blown-out window of a BMW that was parked outside the Fir Tree pub, and the firearms and ammunition found in the loft of a Croxteth teenager. One of those guns, the prosecution allege, was the murder weapon.

The witness said swabs were taken from the barrel and chamber of the Smith and Wesson revolver and Type Two residue was found in both. There was also additional tin in the residue, which, the expert said, was unusual and seen in less than 5% of cases they see in the lab.

Several .45 Colt cartridges, also found in the loft in a bag alongside the gun, were test-fired and found to give off Type Two residue, the same as was found on the gun, the court heard.

Rhys’s football shirt was swabbed and around the bullet hole in the back, where the bullet struck the schoolboy, Ms Shaw found a moderate level of Type Two containing elements of tin.

She said: “It suggests that the cartridge fired from the gun could be the source of the residue on the football top.

“The presence of tin is seen in less than 5% of the residue we see in the lab.”

Ms Shaw also examined clothing taken from the home of defendant Boy M, swabs from Boy M and Sean Mercer, and parts of Mercer’s bicycle, but found no FDR at all.

She explained that, through time and wear, gunshot residue can be worn away and so the samples may have once had FDR but not by the time they were sent to her for testing.

But when questioned by Mercer’s barrister, Richard Pratt, QC, she admitted the Smith and Wesson revolver was “unlikely” to be the murder weapon because of inconsistencies between the results from Rhys’s wound and from the window of the blown-out BMW.

Ms Shaw explained 13 particles of Type One residue and just one of Type Two were found among glass from the BMW hit by the first bullet.

No Type One residue was ever found in the alleged murder weapon at all, Ms Shaw said.

She added: “The expectation would be that both Type One and Type Two would be found.”

Neil Flewitt, QC, prosecuting, asked: “Is one possibility that we have got the wrong gun?”

The expert replied: “That could be a possibility”.

Mr Flewitt then questioned the expert over other explanations for the absence of Type One residue in the gun.

She said the most likely explanation for the absence of any Type One particles found in the British military weapon would be that other shots had been fired in between the August 22 shooting and its discovery on September 30 – removing the Type One residue.

When cross-examined by Mr Pratt, she agreed her findings were consistent with the revolver not being the weapon that had left residue on the BMW.

He said: “If the [revolver] was not fired after this incident and was found in the same as it was on August 22, in your professional opinion, although not impossible, it is unlikely it was the weapon that was used to kill Rhys Jones.”

Ms Shaw responded: “It is not impossible given the possibility there are some other explanations. I would say it is still possible this was the gun.”

But Mr Pratt continued: “But it is unlikely this was the weapon used to kill Rhys Jones?”

She answered: “Precluding all other possibilities, then yes.”