A girl scout was stabbed in the back by mistake after her killer attacked "the wrong people", a court has heard.
The comment was made by Manuel Petrovic, 20, one of four accused of the fatal stabbing of Jodie Chesney in Amy's Park, Harold Hill, on 1 March.
While on remand over the killing, Mr Petrovic protested his innocence, saying he was only asked to drive to Harold Hill, and not why.
A transcript of a secret recording made by prison authorities was read out.
In the 24 May prison recording he told his friends: "I'm going to say I'm a drug dealer, I broke the law with my driving and s***.
"I ain't going to go guilty for something I have not done. I'm no murderer," the Old Bailey jury heard.
During a second visit on 3 August, Petrovic allegedly said to a friend that 17-year-old Jodie was stabbed after his co-defendant Svenson Ong-a-Kwie was "cheffed" (slashed with a knife).
According to the transcript Mr Petrovic said: "They went to bang out on their ops (opposition) and banged out the wrong people."
Asked how he knew that, he replied: "Uh? Because I know that ... It was to do with Svenson's op - they cheffed him up a couple of month or something, a couple of months before.
"He went to ride out and rid out on the wrong people in the park and they thought it was them because they chill in that area.
"That's why she got it from behind," he added.
Jodie was stabbed in the back while sitting with friends in an east London park on the evening of 1 March.
Mr Petrovic denies murder along with Mr Ong-a-Kwie and two youths aged 16 and 17, from east London.
The court heard Mr Petrovic had convictions dating back to 2013 including for possession of cannabis and handling stolen goods.
Mr Ong-a-Kwie had pleaded guilty to possession of class A and B drugs when he was 16 years old.
He also had a conviction for the supply of cocaine and having stolen goods.
According to agreed facts read to court, the 17-year-old defendant, then aged 14, had been involved in an incident in a shop in which a member of staff was attacked with a screwdriver.
The youth went on to plead guilty to assault occasioning actual bodily harm and possessing a pointed article.
The trial continues.