Last night, Crimewatch covered the case of Lisa Hauxwell: a sex offender who could be living as a either man or a woman. On the run from a 14-year prison sentence, the offender has not been seen since being convicted of a string of rapes and sexual assaults committed between 2001-2002.

It has become, sadly, typical to hear of appeals for information on male sex offenders - yet when the perpetrator is female, it always seems much more shocking. But why? The fact is most people know very little about female perpetrated sex crimes and what they do know is often far from accurate.

Female sex offenders are viewed as a rare and peculiar phenomenon, but this is far from the truth. Determining how common female perpetrated sexual offending is a very difficult task, but an international study last year found that the proportion of sex offenders who are female is higher than previously thought. Although they constituted 2.2 per cent of sexual offences officially reported to the police, the rates discovered in victimisation studies were six times that amount. That means more than one in nine sexual offences are committed by women.