The head of the Garda Ombudsman Commission says it can investigate complaints against gardaí that go back years if it is in the public interest.
Mr Justice Kevin Haugh said the commission expects to receive around 4,000 complaints a year but will only be able to investigate around 200.
The commission will begin receiving complaints tomorrow morning.
In future, investigations into alleged garda malpractice or corruption will be investigated not by gardaí, but by independent investigators drawn from financial and legal circles in Ireland and from police forces abroad.
A complaint must be made within six months of the incident but it can go back further if that is deemed to be in the public interest.
The commission will also have a special in-house investigation team to deal with complaints against gardaí involving serious injury or death.
The commission expects to take on around 80 files from the Garda Complaints Board which it replaces, and its investigators have the powers of gardaí.
They can arrest and question members of the force and if, for example, investigating suspected drug trafficking can detain them for up to seven days.
