When the investigation into Michael Jackson‘s death stalled a few months ago, the King of Pop’s oldest son Prince made an emotional plea to detectives to get justice for his late father, The ENQUIRER has learned exclusively.

And in what could be a major breakthrough for prosecutors, the brave 13-year-old has offered to testify against his dad’s personal physician, Dr. Conrad Murray, who was formally charged with involuntary manslaughter on Feb. 8.

"It’s possible Dr. Murray would never have been charged if it wasn’t for Prince’s impassioned appeal to police a few months ago to ‘get justice for our daddy,’" revealed a source close to the investigation.

"The police were giving an update to some members of the Jackson family. When it appeared they could not offer a date when Dr. Murray would be arrested, Prince, who’d been listening outside the room, entered.

"He surprised detectives with an emotional statement. Prince told them ‘not to give up’ and said their father had told him and his sister Paris many times that ‘anything is possible if you want it hard enough and you work hard enough.’

"Prince even offered to testify against Dr. Murray because he said, ‘I was there – it’ll be in my memory forever.’

"The hard-nosed detectives were practically moved to tears. The investigation picked up – and Prince is to thank for that."

Added a Jackson family friend: "Prince is the only person, aside from the doctor, who saw what really happened – and he says he thinks that the doctor did something wrong, that he killed his dad!

"Prince says he saw blood on his father’s clothes, and there were times the doctor would not let him and the other kids in the bedroom to see their dad."

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