The cases that look set to be prioritised include that of 13-year-old Philip Cairns, who disappeared close to his home in Rathfarnham, Dublin, in 1986.

A new team of officers will also examine the case of Stephen Hughes-Connors, the 12-year-old who burnt to death after the hut he was playing in was deliberately set alight in Tallaght in 2001.

The unsolved murder of Frenchwoman Sophie Toscan du Plantier will also be reopened, and it is thought that the disappearance of Mary Boyle, who went missing from her grandmother's house in Donegal 30 years ago, will also be looked at.

Garda commissioner Noel Conroy recently decided to prioritise high-profile unsolved cases to see if new scientific and technological advances could be used to aid in solving them.

A small number of gardai have been working on some cases over the past 18 months on a pilot basis and this will now be extended into a dedicated unit. A policy for the unit is being devised and it is hoped it will be up and running in two months' time.

Senior garda management believe that more sophisticated DNA information, blood pattern analysis techniques and the ability to pinpoint mobile phone calls through masts could give new life to hundreds of stale investigations.

It is hoped that once the backlog of old investigations has been cleared, each murder case will be revisited every year on its anniversary.

Appointments

Conroy has appointed chief superintendent Paul Hargadon to oversee the reviews; detective superintendent Christy Mangan will be in charge on a day-today basis. It is expected that a fulltime staff of around 15 NBCI detectives will work in the new unit and they will be assigned there over the coming weeks and months.

"The way we investigate crimes has been very successful over the years but new technology has to be embraced and this is essentially what this new unit will do, " said a senior garda.

"It is envisaged that this unit will be able to take delivery of every shred of documentation from an unsolved inquiry and instantly use new computer systems and technology to reassess even the tiniest aspect of it. That is in no way a criticism of how a crime was originally investigated but technology has come on so much in less than 10 years that new ways of doing things could easily crack an old case.

"They have been examining cold cases in the US for years and it was only a matter of time before it transferred here. We do not want to give unnecessary hope to families of people affected. There is no guarantee that crimes will be solved but we will be doing our best.

"It is very early days yet and we haven't decided on what cases we are going to focus on initially but there are some obvious ones. Murders will probably be the main ones at the start but it will spread.

Every unsolved crime is technically a cold case. It will all become far clearer in the next few months but it is very exciting, " added the source.

Detectives assigned to cold cases will travel to Britain and Germany to train for their new roles. It is envisaged that they will use a system known as Holmes, the Home Office Large Major Enquiry System. This computer system replaces the usual paper-based investigation and collects and manages vast amounts of information, making it easy to access and collate. At present all garda statements and intelligence reports are taken manually and can run into thousands of documents in a big inquiry. Two or three officers are assigned to read all these reports and decide on what areas deserve priority.

This system is prone to human error and tiny but potentially significant areas of an investigation can be overlooked as a result of the sheer number of documents that need to be read and analysed.

In contrast, the Holmes system can call up and match key words in seconds.

If a red car is seen by a witness in a murder investigation Holmes immediately summons any previous mention of a red car, as well as a description of the person driving it and any other relevant information. Detectives can then instantly identify and focus on any important information.

Crimes have been solved more quickly and detection rates have improved since Holmes was introduced in the UK.