The Garda Ombudsman Commission has sent a file to the DPP on its inquiries into the Kieran Boylan drugs case.
The commission launched a public interest inquiry after drug trafficking charges against Boylan, a convicted drug dealer, were dropped by the State.
The inquiry has been carried out over the past four years but has now been completed.
The DPP will determine whether any further action is warranted as a result of its conclusions, including possible criminal charges. It is the longest inquiry carried out by the commission, which has never officially identified Boylan as the man at the centre of its investigation.
Boylan was sentenced to five years in jail after he was caught with €700,000 worth of cocaine and heroin. While on bail he was arrested in connection with the seizure of drugs worth €1.7m in October 2005 but the charges were then dropped without explanation.
The decision to withdraw the charges was examined by the commission as well as his relationship with the gardai, the level of information he gave as an informant and whether he was officially registered as one.
It also looked at a case where a drugs possession conviction was secured by gardai to establish if Boylan had supplied any information to the authorities.