Apologies if I'm wrong but I researched this once before, right down to looking at the area of the crash, and I recall some decidedly not straight roads.

From a 1987 article:

Among those who mourn the deaths of the women is Broderick himself, who was released on $4,075 bail and came home hobbling on crutches, looking pale and gaunt. He described their deaths as a “terrible, terrible thing.” Of his own physical condition he said, “I’m okay. I’ll be all right.” Asked whether he caused the accident by driving on the wrong side of the road—a common error of visitors to the British Isles, where the correct side is the left—he replied, “Nobody knows yet. I can’t talk about that too much.”

Anna’s husband, John, said of Broderick, “We have no hard feelings toward him. He has to live with this the rest of his life.” Martin added, “I hope God gives him strength. This is a big ordeal for himself as well.”

What exactly took place on Aug. 5 might or might not be known to the Royal Ulster Constabulary. The police are forbidden by law to talk about the accident. There had been some rain, but there were no skid marks. Visibility was good. A witness who had followed Broderick’s car earlier (but did not see the crash) said he was driving at a reasonable speed. A New York City official who specializes in traffic offenses says that if a confused foreigner caused a similar accident in the United States, he most likely would not be charged with a crime. He would only be brought to trial if there was some indication that he had acted recklessly.

Yeah. Lock him up.