Patrick O'Mahoney, head doorman at Raquel's nightclub in Basildon, Essex, at the time Leah died, claimed it was a man named Mark Murray who was now living in Spain.
But Mr O'Mahoney said he ultimately laid the blame for Leah's death at the door of the club's managers, who he said were aware dealers operated in the club and instructed doormen to let them carry on.
The jury at Norwich Crown Court was also told that security at Raquel's had been organised by Tony Tucker, who was one of three men later found shot dead in a Range Rover at Rettendon, Essex.
The court has been told the ecstasy that killed Leah was bought via a network of friends including 18-year-old Steven Packman, of Laindon, Essex, who denies being involved in the supply of the drug. A 19-year-old, Stephen Smith has admitted a similar charge.
Leah collapsed into a coma shortly after taking one of the tablets at her 18th birthday party at her parents' home in Latchingdon in November last year. She died a few days later.
Mr O'Mahoney said police had arrested and questioned Mr Murray following Leah's death. "The police are well aware about Mark Murray," he said. "I am just sick of that scumbag sitting in Spain." Mr O'Mahoney said nine people were in prison because of Mr Murray.
The court was told how the News of the World newspaper had arranged for Mr O'Mahoney to meet Mr Packman in an attempt to hear what the 18-year- old had to say about the ecstasy which killed Leah.
Mr O'Mahoney tape-recorded the conversation. And he said he realised that Mr Packman had bought the drugs from Mr Murray during the conversation. "It could only be Mark Murray really," said Mr O'Mahoney. "When he [Packman] described him I knew who he was talking about. It is probably why no one has seen Mark Murray since that day."
Mr O'Mahoney admitted that he was a criminal and had had dealings in the past with "serious criminals".
He had many convictions, including convictions and had served time in prison. But he said in the last 18 months he had changed his way of life. He said he now lived in fear of his life because he was giving evidence and had given information to police.
He told the court that security arrangements at Raquel's were managed by Tony Tucker, a known drugs dealer, who was found shot dead with two other dealers a few weeks after Leah's death. A trial is pending in connection with the killings, the jury was told.
"I feel sorry for [Mr Packman]. He is afraid of the ghost of Tony Tucker. He should just name the man he is protecting," Mr O'Mahoney said.
"I was aware as well as the management were aware and everyone else was aware what particular person was supplying ecstasy in that club."
The hearing continues today.