It was the sweat that alerted police to the three men.

Christopher Lin, a 21-year-old engineering student from Beverly Hills, had left the Midnight Mafia dance festival at 10pm and was standing outside the gates when police noticed how sweaty he was, despite the cool May evening.

All three men have pleaded guilty to their roles in the supply of MDMA at Midnight Mafia. Credit:Viki Lascaris

Lin, who court documents say was "well known" to police as an MDMA dealer in Sydney's dance festival scene, also seemed "extremely nervous".

When police searched him they found $10,020 stashed between his pockets and his Louis Vuitton carry-all.