The public inquiry into the crimes of British doctor Harold Shipman has heard his victims would have been dead within minutes.
Dr Shipman, (55), of Hyde, Greater Manchester, was convicted in January 2000 of murdering 15 elderly female patients with lethal injections of diamorphine.
The inquiry in Manchester, chaired by High Court Judge Dame Janet Smith QC, is investigating the deaths of another 459 of his former patients.
On the second day of the hearing Dr Henry McQuay, professor of pain relief at Oxford University, said patients injected with 30mg or more of the drug would be dead within 10 minutes or less.
He said the diamorphine would take effect within minutes, causing the person to stop breathing.
"If you do not breathe for three minutes then your brain will be starved of oxygen and you will die."
PA