When 30-year-old Colin Whelan contacted the emergency services on 28 February 2001 informing them that his wife was lying dead at the bottom of the stairs it looked like a tragic accident.

It appeared that Mary Gough had slipped and fallen.

In the months before Mary's death Whelan did extensive internet research into how to get away with murder. As his wife of less than a year got ready for bed, Whelan sneaked up behind her and strangled her with his pyjamas. He then threw her body down the stairs. All the research was in vain though, and Whelan was soon charged with Mary's murder.

On 12 March the computer analyst drove his car to Howth Head where he apparently committed suicide. In fact, Whelan secretly boarded a flight to Mallorca after stealing a neighbour's identity. For the next 16 months he worked in a bar serving hundreds of Irish tourists who knew nothing of his secret past. One eagle-eyed tourist spotted him working and contacted gardai. He was extradited and charged with Mary Gough's murder. He was found guilty by a unanimous verdict and is now serving a life sentence.

Catherine Nevin, the 'Black Widow', is one of the country's most infamous killers, even though she didn't personally murder anybody.

Nevin paid one or two unknown people to murder her husband Tom at their pub, Jack White's Inn, on 19 March 1996.

Nevin claimed to be in bed when she was approached by a hooded man demanding jewellery. She was bound and gagged and when the intruders left she raised the alarm.

By the time gardai arrived her husband was dead, having been shot at close range with a shotgun.

Nevin's story did not add up and even before Tom Nevin was buried, there were rumours that she had ordered his murder. The marriage was certainly in trouble and gardai discovered that Catherine Nevin had previously tried to hire three men to kill her husband.

During her trial Nevin falsely claimed that her husband was a member of the IRA and an alcoholic. It took five days for the jury to find her guilty of his murder. She was also convicted on three counts of soliciting men to kill her husband. She was sentenced to life imprisonment for the murder and three ten-year terms for soliciting.

Frank McCann was regarded as a pillar of the community. He was a family man and senior official in the Irish Amateur Swimming Association with a pretty young wife and an 18-month-old child, Jessica.

McCann arrived home from work on 10 September 1992 to find his home at Butterfield Avenue in Rathfarnham on fire. His 30-yearold wife Esther and Jessica were inside the house and both perished.

At first it seemed a tragic accident but an investigation revealed that the blaze had been planned; the gas had been tampered with to cause an explosion.

Frank McCann was soon nominated as the chief suspect. He had secretly impregnated a 17-year-old after meeting her at a swimming meeting. Jessica was not the couple's child and they had been trying to adopt her, but the application was turned down after the mother of the teen he had an affair with informed the adoption board. He decided he wanted his wife dead and would claim the insurance money. A garda investigation revealed that McCann had previously tried to murder Esther and his story about coming home to find the house on fire was exposed as a lie. He was convicted of the two murders and sentenced to a double life sentence in 1996.

In May 1994 the body of Philomena Gillane was found in the boot of her car outside Athlone train station. The Galway woman had been shot in the back and stabbed six times with a steak knife. She was seven months pregnant and had been reported missing a week before.

In January of that year the dead woman's husband, Pat Gillane, drove to Dublin, stopped two homeless people on Thomas Street and asked them to "do a job for him".

The job involved killing his wife.

The men refused but 35-year-old Gillane did manage to find somebody who would do the job for him.

He was found guilty of soliciting two men to murder his wife and was sentenced to eight years in prison.

Judge Joseph Matthews said it was difficult to imagine "a more vile and vicious crime". Philomena Gillane's mother died in court after collapsing during the trial.