Drugs experts on Guernsey who copied an online recipe for methylamphetamine during a court case have warned the mixture could kill.
The warning comes after a couple were jailed for creating a "crystal meth" production lab in their Guernsey flat.
Dr Roland Archer and his team followed the method used by Wesley Guilbert to prove it could work.
Guernsey Police said they hoped the jail terms for Guilbert and his wife Jennifer would deter other users.
'Not so lucky'
Dr Archer said his team had produced methylamphetamine in the lab to prove the reaction would actually work.
"You can't very well say this manufacture has happened when you don't think it would work.
"We have gone through a lot of them, most don't work at all and some are extremely dangerous.
"Anyone that has followed some of these procedures may have just been lucky, a second time they may not have been so lucky."
Senior Investigation Officer, Rebecca Falla, said there had been a growing trend towards the use of psycho-active substances.
She said: "People will always take the opportunity to try different things."
Ms Falla added: "The landscape of drugs has changed significantly in the last few years and there are lots of things that can be bought and made without us knowing what they really are."
Wesley Guilbert was jailed for nine years for five drugs charges including producing a Class A drug at his Union Street flat in St Peter Port.
His wife Jennifer was jailed for four years for three drug offences - none relating to production.
Det Sgt Jason Savident, from Guernsey Police, said he hoped the conviction would deter anyone considering making or taking crystal meth in the Bailiwick.