The public perception of terrorists like the Omagh bombers is that of anti-social psychopaths.
They are thought to lack emotions and therefore feel no remorse over what they have done.
But studies have shown they are more than capable of emotional responses.
They suffer guilt, self-doubt and are capable of feeling the same horror that others feel when they see the aftermath of another bloody bombing.
What prevents them allowing these feelings to surface are the depths of their political beliefs.
The very nature of a planned bombing introduces complex factors which help enable a terrorist to distance himself from the atrocities carried out.
John Horgan, a lecturer in forensic psychology at University College, Cork, specialises in republican terrorism.
He said that a strong element in any form or terrorism is the psychological distance which the perpetrators put between themselves and the act they are about to commit.
Mr Horgan said: "There are a number of ways that people can hide from the horror of the atrocities they commit.
"The people who put the bomb in the car, for instance, would have been nowhere near the area when the bomb went off, so are distancing themselves from it right away.
"Another major element is the telephone warning. What they are saying is, `We've planted the bomb, we've told you about it, now it's up to the security forces to sort it out.'
"They are putting the blame on someone else. This externalisation of responsibility is a big factor in terrorist groups."
Another aspect of the complex array of emotional armoury terrorists use to protect themselves from guilt lies in their role as protectors of the Irish people. …