Among the cases requiring Neil's expertise was that of Susan Kent in Medway, Kent, in 1999.
The single mother was found raped and tortured to death in her home, apparently by a practised sadist who could have struck again.
Police investigations led to David Ferguson, who had met Susan Kent and also had an interest in the type of sadism practised on her.
He had been questioned early in the inquiry but was released because of a cast-iron alibi as he had been seen at a tattoo parlour on the day of the killing and had picked up a prescription at a chemist shop.
The prescription computer-generated label put him in the pharmacy at the time of the murder.
Barrett took away the chemist's computer for examination and discovered the owner had forgotten to change the time and date printout when British Summer Time ended, making the label one hour out, destroying the alibi and securing Ferguson's conviction.
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