I should point out that, as someone who has watched countless episodes of True Crime shows, an abuser, especially with sociopathic tendencies which Brian appears to have, can come of as the innocent party when indeed he's not. And abused people, especially those with anxiety and abandonment issues, such as Gabby, will often lie and say they weren't abused to protect the abuser. So while is may be somewhat understandable that the police assumed Gabby was the abuser in this situation, it is very likely that Brian was. And as I said earlier, the policman may have been biased because of his own personal situation.
You are ignoring the cut and scratches.