When Reynhard Sinaga took a victim back to his flat, he would drug them unconscious before launching his assault.
Although it is sometimes referred to as a date rape drug, GHB gamma-hydroxybutyrate is actually used recreationally and consensually. It is fairly common for gay men to use it during chemsex - when drugs are used to enhance sex between two or more partners - but it is also used by heterosexuals as a party drug.
But rapists use GHB as a weapon - one recent survey estimated more than a quarter of those polled were sexually assaulted whilst unconscious. GHB is a separate but almost identical drug to GBL gamma-butyrolactonea substance sold legally as an industrial solvent but which becomes GHB once it enters the body.
Together the drugs are known as "G", and both come in the form of a clear, odourless, oily liquid that is diluted in soft drinks and swallowed. G can give users a feeling of euphoria and can increase their sex drive. But increasing the dose by a fraction, even less than a millilitre, can be fatal. Overdosing on G - which is particularly easy when it is mixed with alcohol or other drugs, and when the strength in bottles varies - can make people incoherent, suffer convulsions, lose consciousness and stop breathing altogether. Professor Adam Winstock, consultant psychiatrist and founder of the Global Drug Survey, warns: "It's a drug that poses huge risks when people are out there trying to use it for fun.
What does it do?
According to official figures from the Office for National Statistics, there were deaths in England and Wales between and that involved GHB. But the total could be much higher - GHB is not part of routine toxicology tests after sudden deaths.
According to Professor Winstock, the drug can be difficult and expensive to detect. It is also difficult to know for sure how many sexual assaults are connected to GHB. Before Sinaga's conviction, perhaps the highest profile case was that of convicted serial killer Stephen Port, who was given a life sentence in for poisoning four young men with lethal doses of the drug.
An additional obstacle to knowing the scale of the problem is that victims often don't report it to the police, says Professor Winstock.
More on this topic
People can feel uncertain about what happened, and whether a crime occurred, he says, as well as shame, guilt and fear "of having to disclose information that they may find very embarrassing", he says. Some also fear they could be investigated for drugs offences. A dependence on G can develop quickly, and Professor Winstock warns that anyone who has taken it daily should not try to stop without medical help.
The long term effects of taking G repeatedly are not yet known. Like many illicit drugs, the prevalence of G is hard to track as it does not feature in national drug use surveys.
What is ghb?
But Strudwick says G is "very easy to find and to buy if you know where to look" because of the "legal loophole" that means GBL can be sold for industrial use - as a paint stripper, among other things. Once sold in large quantities, it can then be distributed and supplied by dealers in smaller quantities through dating apps such as Grindr," he says. GHB was developed in the s as an anaesthetic, but was discontinued because of its side effects.
During the s, it was used as a sleep aid and a supplement for body building. Although GBL is used legally in industry, it has also been a Class C drug sinceand anyone who supplies or possesses it, believing that it will be consumed, is breaking the law.
Possessing either drug can warrant up to two years in prison with or without an unlimited fine, and supplying can result in up to 14 years with or without such a fine. Dr Winstock says that increasing the class would make "absolutely no difference" to its usage, and would discourage people from seeking help.
Instead he says the government should focus on educating people so that drugs can be used more safely, and on promoting "honest conversations" about their use.
The family of Eric Michels, who was murdered with an overdose of GHB inhave been campaigning for the drug to be reclassified as Class A. His son Sam told the BBC it was "a really, really dangerous drug" which had killed multiple people, including his dad. If you have been affected by the issues raised in this article, help and support can be found at BBC Action Line. The sexual predator who waited outside nightclubs.
What is GHB? What does it do? How many deaths have been linked to GHB? And sexual assaults? Is it addictive?
How common is it? Where does it come from?
Is it illegal? Related Topics.
Reynhard Sinaga. More on this story. Published 6 January