The mother of a teenager who died after taking a lethal painkiller has welcomed tougher guidance on prosecutions involving the drug.
Michelle Fraser has been campaigning for stronger laws for dealing in fentanyl since her son, Robert, from Deal, died from an overdose aged 18.
Although available on prescription, it is increasingly being sold by dealers and has killed thousands in the US.
Ms Fraser said the guidelines were "an amazing step forward".
Until now there has been no specific advice for lawyers to take into account when bringing fentanyl-related prosecutions.
But after lobbying from Ms Fraser and her MP, Charlie Elphicke, the Crown Prosecution Service has included a section on the painkiller - which is 50 times more powerful than heroin - in its latest guidance on drug offences.
- Synthetic opioid related to heroin but more than 50 times as powerful
- Can be prescribed under supervision but often mixed with other drugs by illicit dealers
- A tiny quantity - as little as 2 micrograms - can be lethal
- Effects of consumption can include euphoria, confusion, a slowdown in breathing, high blood pressure and unconsciousness
- There were 58 fentanyl-related deaths in England and Wales in 2016 - nearly three times the figure four years earlier
Source: Crown Prosecution Service/Home Office
It advises prosecutors that as little as 0.002g of the drug is potentially fatal - which they should take into account when deciding what category of charge to bring.
It says the dangers of fentanyl - "even in small quantities" - should be brought to the attention of the court, and its relative potency compared with heroin or morphine should also be spelt out.
Ms Fraser, who ultimately wants dealers to be charged with manslaughter if they supply the class A drug to someone who subsequently dies from using it, says she is delighted with the development.
She said: "Fentanyl isn't [just] a class A drug. Fentanyl is a killer. And now when looking at the guidelines on prosecuting people, the potency of the drug involved has to be taken into consideration.
"It is an amazing step forward."
Mr Elphicke, MP for Dover, said: "What we have seen today is the first etching of Robert's Law, with the prosecutors' guidance.
"I hope that the Sentencing Council will review sentencing to make sure that people who are dealing in fentanyl get tougher prison sentences so that we can stamp out this dangerous drug."