In October 1999, Warren Blackwell was convicted of indecent assault. He had, it had been alleged, raped a woman at knife-point on New Year’s Eve. He served more than 3 years in prison for this alleged crime. The conviction was overturned, well after his release, this month.

Mr Blackwell’s conviction was quashed because the credibility of his accuser was undermined. His initial conviction rested in large part on the testimony of his alleged victim. Once an investigation by the Criminal Cases Review Commission had damaged her reputation, her testimony was no longer deemed sufficient grounds for a safe conviction. The verdict on Blackwell was changed, belatedly, to ‘not guilty’.

The accuser, it turned out, had a history of making rape allegations. She had previously accused at least five men of rape, but never before had her claims been substantiated.

It would be dangerous to argue from the mere fact that a woman has alleged rape on a number of occasions without her alleged attackers ever being prosecuted to the conclusion that she is a serial liar. The conviction rate for rape is only 5%, and this is plausibly due to difficulties in proving guilt beyond a reasonable doubt rather than because most allegations are spurious. A woman might genuinely be raped several times without getting justice.

However, in this case there was enough to call the accuser’s credibility into question. Not only had she made an unusual number of accusations in the past, but at least one of those accusations had been conclusively disproven. She had a history of making false allegations, a track-record of lying.

This case illustrates the importance of reputation in establishing a witness’s credibility. If someone is known to have lied in the past then their credibility is reduced, particular regarding similar claims in similar situations. Once the facts about Blackwell’s accuser were revealed, the case against him was substantially weakened, and he was rightly treated as a victim of a false accusation rather than as an assailant.