Irish police will look to DNA testing to link Mark Hennessy to unsolved crimes in past 20 years as they believe the violent murder of this 21-year-old student was not his first crime.

Ireland’s police are investigating the possibility that Mark Hennessy, who violently kidnapped and murdered a 21-year-old accountancy student Jastine Valdez in broad-daylight, could be linked to unsolved violent crimes in the area over the last 20 years.

On Saturday Hennessy kidnapped Valdez, punching her and bundling her into his Nissan X Qashqai, Enniskerry, County Wicklow. Her beaten body was found in thick woodland in Rathmichael, South Dublin, on Monday.

Fundraising effort launched to assist parents of Jastine Valdez https://t.co/M1m4piu8b5 pic.twitter.com/MViBai3nHS

— Independent.ie (@Independent_ie) May 22, 2018

Hennessy was shot by police on Sunday night. The police ombudsman is investigation he shooting but one line of investigation is that Hennessy lunged at the police officer with a knife.

The police believe that such a horrific crime, the public kidnapping and brutal murder of a woman, is unlikely to be a first-time offense. It is being reported that Hennessy’s DNA will be crosschecked with evidence from historic crimes and disappearances in the Leinster area over the last 20 years.

There are several cold cases related to missing women in the area including Fiona Pender, Annie McCarrick and Jo Jo Dullard. Also, in 1999 Raonaid Murray was stabbed to death close to her home in Glenageary, South Dublin, which is close by. The Mirror reports that Murray’s murder case may be reexamined.

This area of Wicklow and south Dublin has was once known as the Vanishing Triangle as so many women were known to have gone missing.

Read more: Ireland reeling after brutal sex attack and murder of Dublin schoolgirl - other kids the suspects

Speaking on Morning Ireland on RTE Radio 1 this morning, crime correspondent Paul Reynolds said: "They have to look at where he was and what he was doing around the time when some of those women disappeared.

"He would have been very young for some of the cases, for example the case of Annie McCarrick who disappeared in 1993, he would have been only 15 years of age.

"But Deirdre Jacob disappeared in 1998 when Mark Hennessy was 20 years of age so they definitely will look at him.

"But they'll also look at him for more recent attacks on women. They'll check his DNA and they will have to consider him even if only to rule him out as a suspect in these cases."

Prayer services have taken place around the country following the disappearance of Jastine Valdez. In Bray, around 200 people attended a candlelight vigil and offered prayers to her family pic.twitter.com/LEdQK5J7kb

— RTÉ News (@rtenews) May 21, 2018

Murdered 21-year-old student Jastine Valdez.