McGee, when questioning Kat, produces what is depicted as a rare 1909 T206 series baseball card for Sherwood "Sherry" Magee (1884-1929) that has his last name misspelled as "Magie". This error was quickly corrected, thus making it very rare. In 2018, this card which was graded "8/10" sold at auction for $660,000.
A few scenes coincide with the storyline of Mystic River, where Kevin Chapman portraited a henceman (Val Savage) to Sean Penn's character.
Billy tells Parker he won't stop trying to find his nephew's killer, because if Parker arrests the killer he will be out in 10 years on good behavior, and that isn't his idea of justice, that his idea is and eye for an eye. Parker might have helped convince Billy to stand down if he had pointed out that the person who murdered Sean also murdered an active duty Navy sailor. Which would make this a federal case, and that the killer would be facing two counts of murder in the first degree, which would equal at the very least a sentence of life in prison without the possibility of parole. But considering that one of the victims was active duty Navy the person in question would very likely be given the death penalty.
In the opening scene, the running kids had stolen three hubcaps, which is pretty pointless. You need four. However, maybe they only managed to get away with three and planned to back later for the other one.