By Alexis Akwagyiram
BBC News Online
The University of Leicester is to conduct a major new study into the experience of stalking victims. Dr Lorraine Sheridan, a psychologist at the university, told BBC News Online about the psychology of the crime.
Stalking can leave the victim emotionally devastated
Having researched stalkers and their victims for the last seven years, Dr Sheridan is widely regarded as one of the UK's leading authorities on the subject.
The psychologist and her team are joining forces with charity Network for Surviving Stalking to conduct a study into how victims are affected.
Dr Sheridan said "there are different reasons for stalking", with no set rules.
She said: "Most stalkers know that it is wrong but want to continue for various reasons. For example, they may crave power, seek revenge or believe they should be with the person they are stalking."
But her research has revealed trends, enabling her to identify four broad categories into which stalkers tend to fall.
Men in their mid-30s are the most common perpetrators of this type of abuse.
Dr Sheridan said: "The biggest group of stalkers are former partners - people who have had an intimate physical and emotional relationship with the victim.
"It is an extension of domestic abuse. It does not have to be physical violence - it could be emotional abuse. "
According to her research, stalkers often fall into the category of "infatuation harassment", harbouring romantic fantasies and pursuing the object of their desire with non-malicious ruses.
Such an approach may be characterised by the stalker quizzing friends and associates for details about the person in question, or hanging around to pretend they have had a chance encounter.
A slightly less common form of stalker may be "delusional".
In this situation the perpetrator may be incoherent, believing "a special link exists between them and their victim", even though there has been no prior conversation between the pair.
Men in their 30s are the most common perpetrators
Their behaviour is often characterised by constant telephone calls, letters and visits to the victim's workplace.
Unlike the "infatuated harasser", this type of stalker may also be sexually suggestive.
In such circumstances, the victim tends to face a high risk of physical violence and sexual assault.
The least common, but perhaps most dangerous, type of stalker identified is the "sadistic" obsessive.
He, or she, has a tendency to focus their attention on a person who they deem to be happy, and therefore worthy of victimisation.
Often combining physical, emotional and sexual intimidation, such stalkers may also broaden their targets to family and friends in a bid to isolate their victim, exert control over the person's life and, ultimately, lower their self-esteem.
Regardless of the stalker's intentions, Dr Sheridan says the effect on the victim can be "immense".
"Victims may suffer from post-traumatic stress disorder to the same degree as people who have experienced an earthquake or airline crash," she said.
She added: "Some stalking can result in violence and even the death of the victim."
Stalking can have other, less obvious, effects on the victim and those close to them.
"The effects can be financially detrimental, as well as physical and emotional," said Dr Sheridan.
"Some stalkers may resort to damaging the victim's property and victims may feel the need to move home or change their job in order to distance themselves from the stalker.
"There can be huge financial effects - people can lose their job and their homes."
Dr Sheridan stressed it was important to spot the early signs of obsessive behaviour and take it seriously.
She said: "Many people do not receive the proper support from those close to them, who may play down the victim's fears.
"The biggest problem is not getting the authorities to take notice, it is for people to realise that they are being stalked in the first place."
She added men were particularly bad at accepting they were being stalked.
Her advice to victims is simple: "If a person believes someone is behaving inappropriately towards them, they should go to the police and try to get something done about it."