“What are the most common signs that there is domestic violence in a home?”

Outward signs of abuse are hearing the actual violence. This may involve hearing physical abuse such as someone being hit or kicked and yelling/screaming. You may also see evidence of physical abuse on someone's body. Sexual assault and abuse, unless witnessed, would need to be gathered by a professional during an exam. Emotional abuse is harder to detect. At any rate, if you suspect someone is in danger call the police to investigate the situation, and they will intervene. It is often difficult to get a victim help if they refuse unfortunately.

Domestic violence is not one size fits all. Contact your local police to express your concerns. Err on the side of safety. Be the change that you want to see in the world.
Blessings to you.