Garda Commissioner Fachtna Murphy has publicly backed the unprecedented decision to shield the former lover of wife killer Eamonn Lillis from the media.

Masseuse Jean Treacy was driven into an underground entrance of the Criminal Courts of Justice to give evidence in her ex's murder trial as more than two dozen photographers and camera crews waited at the front doors.

Commissioner Murphy said a court witness should have the right to privacy despite having to give evidence in public, adding he would authorise similar protection again if it was needed.

"For some time now I have been asked about the difficulties of investigating and prosecuting murders and other serious crimes where fear prevents the community from offering information or evidence to gardai," he said.

"In the main, this fear is born out of concern for physical or personal safety.

"It would be a grave development if individuals were also to be dissuaded from contacting gardai with valuable information or evidence because of an anxiety or fear that their privacy would be the price exacted for their contribution."

Lillis was jailed for six years and 11 months last Friday for the manslaughter of his advertising executive wife Celine Cawley at their home in Howth, north Dublin, in December 2008.

The 52-year-old had his bail conditions altered six months before the trial, with a judge warning him not to approach Ms Treacy. It is understood gardai were unwilling to allow him and his former mistress use the same entrance at the courts.

Commissioner Murphy said the decision was based on Ms Treacy's needs and circumstances.