Man and woman plead guilty to the manslaughter of an 80-year-old man from the Cotswolds

A man and a woman have pleaded guilty to the manslaughter of an 80-year-old man from the Cotswolds and a 37-year-old man from Banbury in Oxfordshire.

Following a joint investigation by Gloucestershire Constabulary and Thames Valley Police, Adina Mihai, aged 31, and Madalin Dumitru, aged 30, both formerly of Ilford in Essex, appeared via video link at Oxford Crown Court this morning (Wednesday 24 June) where they pleaded guilty to the manslaughter of both men.

The pair also entered guilty pleas to two further counts each of administering poison.

Between August 2024 and July 2025, Mihai and Dumitru targeted men who were seeking sexual services in order to steal from them.

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, aged 80 and from Bagendon near Cirencester was found dead in his property on 21 August 2024 and Gary Mouat, aged 37, was found dead at his property in Banbury on 13 July last year (2025).

Following a post-mortem examination, detectives from Thames Valley Police Major Crime Unit ascertained Mihai had poisoned Mr. Mouat with GBL after secretly adding it to an alcoholic drink.

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

Through forensic links this led Gloucestershire Constabulary’s Major Crime Investigation Team to conduct further enquiries into Mr. King’s death, which was initially deemed to be non-suspicious due to a pre-existing health condition he had.

Further toxicology tests revealed Mihai had also poisoned Mr. King with GBL.

Thames Valley Police also discovered two surviving victims from across the south of England, who Mihai and Dumitru had also drugged and stolen from.

The pair were arrested on 31 July last year and charged on 6 August last year following Mr. Mouat’s death.

Mihai and Dumitru were further charged in relation to Mr. King’s death on 24 April this year (2026).

Gloucestershire Constabulary’s senior investigating officer, Detective Inspector Adam Stacey, of the Major Crime Investigation Unit, 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.

“The tireless work of all those involved in the joint investigation left Mihai and Dumitru with little choice but to plead guilty to manslaughter and administering poison in the face of overwhelming evidence.

“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.”

Thames Valley Police’s senior investigating officer, Detective Inspector Michael Roddy, of the Major Crime Unit, said: “This has been an extremely complex and resource‑intensive investigation, involving specialist teams across Thames Valley Police, Gloucestershire Constabulary and partner agencies so I am proud to have this positive result.  

“Adina Mihai and Madalin Dumitru used drugs to incapacitate men who had been seeking sexual services, before stealing from them. 

“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 date to be determined.

ADINA MIHAI

MADALIN DUMITRU