When Niko first meets Gerry, he is heavily inebriated, making him very capricious. He belittles his brothers and Michael Keane, a friend of the family. Immediately after, he warns Niko to never hurt his family, or he will hurt Niko's. It is hard to decide whether or not to like Gerry when judging him solely on his opening scene.
Later after that mission he calls Niko saying he has work. Niko comes over to visit a now sober Gerry. He is much warmer to Niko during this meeting. In the mission, Undertaker, it's shown that he was taken to jail. After the funeral he calls Niko saying that he has him on the visitors list at Alderney State Correctional Facility. He tells Niko to kidnap Gracie Ancelotti, the daughter of Giovanni Ancelotti. Even though Gerald harbors hopes he will be released from prison, the charges against him prove to be more severe than he knows. Gerald bids farewell to Niko, as he will be spending a long time in prison.
There is some speculation that Gerald escaped from prison during the mission Get Lost in the expansion pack, The Lost and Damned. During the shootout in the Alderney State Correctional Facility, prisoners can be seen escaping from the prison and it is deemed possible that Gerald is one of these escaping convicts.