A judge issued a warning on the perils of mamba to the city's homeless people.
It came after David Whitely appeared in court on his 44th birthday and admitted having the drug.
District Judge Tim Spruce said: "There is a lot of mamba on the streets and no-one really knows what that drug can do.
"You have been out of trouble for 13 years and you have pleaded guilty straight away."
He gave Whitely one day in custody which was "deemed served" because he had been in police cells from Sunday afternoon until Monday.
The drug must be destroyed but Whitely was excused £85 prosecution costs and other cash penalties.
He said he had been on the streets for a fortnight. When asked about the drug, Whitely said: "Crazy, crazy.
"I have only touched it since I have been homeless. I want to get somewhere but they keep offering me a shared house.
"That is a problem because people start picking on me. Me and a lad are trying to get one place so I can be his carer."
He pleaded guilty to having the drug - listed as a synthetic cannabinoid in the charge - on Carrington Street on July 17.
Mr Kwok Wan, prosecuting, said Whitely was caught in a police operation.
"A plain clothes officer was taking part in a pro-active exercise looking for anyone using the drug in that location.
"He was the one person there at the time," added Mr Wan.
He said Whitely was last in trouble in 2006. Whitely said that he does not receive any state benefits.
