A woman posed as a sex worker and administered a deadly amount of sedative to two men so that she and an accomplice could steal from them.

Adina Mihai, 31, and Madalin Dumitru, 30, admitted the manslaughter of an 80-year-old Gloucestershire man and a 37-year-old from Oxfordshire.

They also pleaded guilty at Oxford crown court to two other offences of administering poison to two other men in southern England, who survived.

Between August 2024 and July 2025, Mihai and Dumitru, formerly from Ilford in Essex, targeted men who were seeking sexual services in order to steal from them. The pair took financial deposits from the victims before Mihai met them at their homes.

Posing as a sex worker, Mihai secretly administered the victims with GBL (gamma-butyrolactone) – a substance that converts into GHB (gamma-hydroxybutyrate) when in the body. GHB is a sedative and sleep-inducing agent.

Malcolm King, 80, from a village near Cirencester in Gloucestershire, was found dead at his home on 21 August 2024, and Gary Mouat, 37, at his property in Banbury on 13 July last year.

After a postmortem examination, detectives from Thames Valley police’s major crime unit ascertained Mihai had poisoned Mouat with GBL after adding it to an alcoholic drink.

Detectives issued a bulletin to all other police forces in the country to share the intelligence in case any other unexplained deaths were linked to the pair.

Gloucestershire police’s major crime investigation team looked again at King’s death, which was initially deemed to be non-suspicious due to a pre-existing health condition. Further toxicology tests revealed Mihai had also poisoned King with GBL.

Thames Valley police also discovered two surviving victims from the south of England whom Mihai and Dumitru had also drugged and stolen from. They cannot be named for legal reasons.

No other deaths, poisonings or thefts have been linked to the pair but police are keeping an open mind about the possibility of other victims.

The pair appeared via video link at Oxford crown court on Wednesday where they pleaded guilty to the manslaughter of both men and to two further counts each of administering poison.

The Gloucestershire senior investigating officer, Det Insp Adam Stacey, said: “Adina Mihai and Madalin Dumitru targeted men who were seeking sexual services and covertly drugged to render them unconscious before stealing from them.

“Tragically for Mr King, their callous and calculated actions had fatal consequences. Our thoughts are with Mr King’s family, at what must remain an incredibly difficult time for them. We continue to support them with our specialist officers.”

Det Insp Michael Roddy, of Thames Valley police, said: “For Gary Mouat, these actions had fatal consequences so I am pleased to have got answers for his family and would like to thank them for their support throughout our investigation.”

Mihai and Dumitru have been remanded in custody and are due to be sentenced at Oxford crown court at a later date. They were told by Mrs Justice Brunner they will receive long jail terms.