The Independent TD Mr Tony Gregory told the Special Criminal Court yesterday that heroin had "ravaged" Dublin's inner city communities for 20 years.
He said he knew of entire families wiped out by heroin and said there had been a community response to the problem.
The Fianna Fail TD was giving evidence on behalf of one of two men who have pleaded guilty to assault and violent disorder following an anti-drugs meeting in Dolphin's Barn.
Mr Josie Dwyer, a heroin addict, died after the assault, and his friend, Mr Alan Byrne, was injured. The court adjourned sentence on the two men until today after hearing evidence from a number of character witnesses including Mr Gregory. Members of the Coalition of Communities Against Drugs picketed the court yesterday.
Ronald Byrne (40), of Cremona Road, Ballyfermot, and Stephen Carney (24), of Dolphin House, Rialto, have pleaded guilty to assaulting and injuring Mr Byrne (26), of Basin Street flats, Dublin, on May 14th, 1996.
They changed their pleas and admitted committing violent disorder after they were re-arraigned on the fifth day of their trial for the manslaughter of Mr Dwyer (41), at Basin Lane. The State is expected to drop the manslaughter charge after they are sentenced on the lesser charges.
Mr Gregory told Mr John McCrudden QC, for Byrne, that he "could not believe that young people were injecting heroin directly into their veins on balconies and stair-wells until mothers came and told me that they had to wash the blood off the stairwells because their children were playing there".
Sister Elizabeth O'Brien told the court she had lived in Dolphin House since 1986 and had seen the effects of the heroin problem. She said there had been very little response from the outside world. She had attended Concerned Parents meetings in the area which Ronald Byrne had chaired and he had given up a lot of his time and energy to dealing with the drugs problem.
The court has been told the two men have already been jailed for 20 months by the Circuit Criminal Court for violent disorder relating to the incident when Mr Dwyer died.