The subway map shown in the beginning of the episode is incorrectly labeled, noticeably misplaced in Brooklyn, and incomplete. The routes/colors are correct, but the numbers and letters are wrong. They say someone got off on the last stop of the 6, but that is actually the 4 line and it continues past there.
Eliot Stabler mentions to Olivia Benson that Fin and Munch are meeting Donovan Black at his residence near City Hall. However when Black exits from the subway where Fin and Munch meet him, an West 72nd Street sign is visible. City Hall is 5 miles south of 72nd Street.
Benson and Stabler have to convince ADA Marlowe to arrest the suspect for raping Sophia so that he doesn't get released and flee the jurisdiction and/or rape another woman but she is hesitant to do so because they don't have Sophia to make a complaint against him. Yet Munch and Fin caught the suspect forcing another pregnant woman to walk with him at knife-point, he threatened her with harm to her unborn baby if she didn't go with him. That means they can arrest him and charge him with: kidnapping in the second degree, a class B felony with a minimum sentence of five years in prison and a maximum of 25 years; criminal possession of a weapon in the third degree, a class D felony with a minimum sentence of two years in prison and a maximum of seven years; and menacing in the second degree, a class A misdemeanor with a maximum sentence of one year in jail. With the suspect's prior criminal record of sexual assault he would either be remanded or be given a high bail amount, and upon conviction he would get the maximum sentence giving them more than enough time to build a case against him for Sophia's rape. So the debate about not having cause to arrest him so he can't get away or harm another woman was redundant.