Episode three of ITV's Little Boy Blue focuses on the mystery of the murder weapon that killed young Rhys Jones and Detective Superintendent Dave Kelly's determination to seek justice for his family.

Kelly is fully convinced of 16-year-old Sean Mercer's guilt, so when a weapons expert tells him the gun they found couldn't possibly be the one that shot the bullet, Kelly orders him to look a little harder.

Rhys Jones - The real story

It's an episode jam-packed with technical talk about forensic science, but what's the real story?

How did the police prove the gun was the murder weapon, used to kill Rhys Jones?

Dave Kelly and his team believed that the Smith & Wesson gun they found in Boy X's loft was indeed the murder weapon, but firearms expert Mark Robinson said it couldn't have fired the .45s sized bullets because it hadn't been designed to do so.

Kelly wasn't convinced, though, so he challenged Robinson to look again and see what he'd been missing.

The firearms expert carried out some tests and discovered that the rifle was capable of firing the .45 bullets that had been found with it. And he also realised that when the .45s were fired by the revolver, they didn't fly 'true'. Instead, they began to tumble through the air, head over tail, creating a much larger entry wound that was almost keyhole shaped.

It was thanks to this revelation – and the discovery of gunshot residue on the back of his Everton shirt – that Kelly and his team decided that Rhys had in fact been shot in the back.

“I thought and everyone thought he was shot through his smaller wound and the larger wound was the exit wound" Kelly told the Liverpool Echo.“I said ‘Listen, that is the gun so you go away and revisit it’. It transpires that it was the other way around. It was a tumbling bullet and that causes the big hole.”

This discovery was crucial when it came to proving the gun found in Boy X's loft was the murder weapon.

What happened to Boy X?

In the ITV drama Kevin Moody (the fictional name given to Boy X) makes a deal with police to identify Sean Mercer in exchange for immunity from prosecution.

This is exactly what happened in real life. In April 2008 the Director of Public Prosecutions granted Boy X immunity and sent him into hiding. He was put under police protection and given a new life and new identity in exchange for his testimony.

Boy X was the youngest person given such protection under the Serious Organised Crime Act 2005, and it was only the second time the police had used the power afforded to them under the legislation.

When were Sean Mercer and James Yates arrested?

Mercer and Yates were taken into custody by police in a series of dawn raids on April 15th 2008 and Mercer was formally charged with the young boy's murder.

Did James Yates really try to make a deal for his parents?

Yates almost immediately requested vulnerable prisoner status when he was taken into custody, thanks in no small part to the rival Strand Gang's hatred for him and the 'Baby Killer' taunting he claimed he'd been subjected to in prison.

It's not clear whether he asked for immunity for his parents, though it was widely reported that he broke down in tears during a conversation about his family with a prison officer. Yates was said to be afraid they would face reprisals.

Who were Melvin Coy and Gary Kays?

There's a lot of talk about Melvin and Gary in episode three. Melvin Coy was the man who drove Sean Mercer away from Croxteth to help him dispose of his clothes and wash in petrol to remove gunshot residue. Kays worked alongside Coy to cover up the crime, but he was also the man who phoned Mercer to tell him that the intended target, Wayne Brady, was on 'Crocky Crew territory'.

More like this

Kays' phone call set the events of that fateful night in motion.