David Canter: Fritzl, like Fred West, believed he was a good man

Josef Fritzl's complaint, through his lawyer, that he is being portrayed as a monster shows the profound depths to which self-deception can reach. Without doubt he does not recognise the horrors to which he subjected his daughter over 24 years and the children he fathered with her in the dungeon he built to keep them. His protestations are like those of many other violent offenders who cast themselves in the role of misunderstood hero rather than villainous monster.

They are reminiscent of more than one rapist who has said to his victim, without any irony, after he had assaulted her, "you should be more careful because someone nasty may have attacked you". These men do not see themselves as criminals. To them, their actions are not as serious as others see them.

Fritzl has a lot in common with Fred West, the Gloucester serial killer. Before he killed himself, West wrote a memoir that was clearly intended to be his account of the life he had lived. In his almost illiterate prose, West starts his memoir, "I was loved by an angel", then goes on to present a picture of domestic bliss that would be at home in a Mills and Boon novel. Never once does he mention his killing of the young women he says he was so in love with, or even the fact that they were buried while still pregnant with his children.

One of the reasons that West and Fritzl got away with their vicious crimes for so long was that their belief in the acceptability of what they were doing enabled them to live an apparently blameless second life, while they indulged their distorted appetites out of public view. They could put on such a good impression of being caring fathers because they believed that's what they were.

While Fritzl should not be allowed to escape any of the blame for the shocking abuse he carried out, his own reference to the standards of fatherhood – as he sees them – helps us to see how his social milieu facilitated his depravity.

Despite the fact that he had spent 18 months in prison for raping a 24-year-old woman and been arrested for other sex offences, his daughter was returned to him by the police when she had run away from home, without any exploration of her reasons. When she then disappeared from public view there was no serious inquiry into where she had gone. The sudden appearance of three of her children (allowed up from their dungeon by Fritzl, who had fathered them) seemed to be accepted by his wife and the authorities without question. Yet this man with his criminal record and strangely growing family was able to run up debts of millions of euros, which are only now being called in.

In the aftermath of the Second World War, psychologists struggled to make sense of how a whole nation could fall sway to the depredations of Nazism. One powerful explanation was that severe upbringing gave rise to what was called "The Authoritarian Personality". These were people who saw the world in very crude black and white terms and accepted arbitrary authority without challenge. Present-day Austria has clearly moved on from such rigid norms, but pockets still exist, as in the Fritzl household, where the father is obeyed without challenge.

Such authoritarianism is not insanity. Serial killers and rapists often claim they are not in control of their actions, but it is very unusual for courts anywhere to accept this as an insanity plea.

The mental clarity with which they carry them out gives them away. Maintaining the dungeon for 24 years in which he could abuse his daughter and her children shows a frightening awareness of exactly what Fritzl wanted to achieve. His claims that he could have killed them but chose not to, and thus was really a good father, is a chilling indication of just how rational, sane but self-deceiving this monster is.

David Canter is director of the Centre for Investigative Psychology at the University of Liverpool. His most recent book, 'Mapping Murder', is published by Virgin Books