The three men, identified as Pakistan bornKhurramShazadButt, Moroccan-origin Rachid Redouane and Moroccon-Italian Yousef Zaghba,all had high levels of a drug called DHEA in their system, according to a toxicologist report presented at a pre-inquest hearing at the Old Bailey court in London.
Counter-terrorism officers had shot and killed the men, who were wearing hoax explosive vests,during the Islamic State (ISIS) claimed terrorist attack on June 3, 2017.
DHEA is available without prescription as a natural supplement and is widely believed to help build muscle.
"Analysis of samples taken from the attackers revealed the presence of DHEA, a steroid hormone, above the acceptable physiological range. These findings suggest use of steroid DHEA recently prior to death in a period ranging from several hours to days before death," Jonathan Hough, the counsel for the inquest, said in a written submission to the court.
The toxicologist will give evidence at the inquest hearings into the death of the victims and attackers, to be held separately and set to begin early next year.
Hough informed the court that the firearms officers who shot the terrorists will seek anonymity at the inquest hearings, and some evidence from MI5 intelligence service may have to be given in secret.
He said that 27-year-old Butt, believed to be the ring- leader of the terror group, had "been the subject of an MI5 priority investigation for almost two years, from mid-2015, and while 30-year-old Redouane and 22-year-old Zaghba had not been under MI5 surveillance, they were associates of Khuram Butt.
Chief Coroner Mark Lucraft said anyone wishing to remain anonymous including the families of the attackers will be required to make requests ahead of the inquest.
"Central London and another iconic bridge...was the scene of shocking events that devastated the lives of many. I hope the (inquest) will provide answers to the obvious and understandable questions that the families have...and give comfort in such difficult circumstances," he said.
A second pre-inquest review is scheduled to take place later this year before the two separate inquests start fully in 2019.
Police, security services, fire and ambulance services will attend the inquests, as well as the families of both the victims and attackers.
During the attack in June last year, the three attackers had ploughed into pedestrians in a white van on London Bridge and then went on a stabbing frenzywith 12-inch ceramic kniveson people on a night out at bars in nearby Borough Market area. The attack lasted eight minutes, claimed eight victims and injured 48 others.
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