this is one of the most ignorant things i hear.     
Woman walks into a police station...   
Woman: My husband beat me up last night, i was scared to call. 
Cop: Do you have any injuries? 
Woman: Yes, here they are.  (Shows some redness consistent with her statement) 
Cop: Did anyone else witness this? 
Woman: No, we were home alone. 
Cop: What do want to do? 
Woman:  I want my piece of shit husband arrested.   
Scenario #1 
Cop: Did you beat your wife up last night? 
Man: (says Nothing) 
Cop: Are you going to answer my questions? 
Man: No, talk to my lawyer. 
Cop: You are under arrest for Domestic Violence.   
Scenario #2 
Cop: Did you beat your wife up last night? 
Man: Nope, my wife was drunk last night and fell down. I wasn't even home last night. 
Cop: Where were you? 
Man:  I was with my girlfriend. My wife found out about us. 
Cop: Copy that.  Will your girlfriend confirm your story? 
Man: Yes. 
Cop:  Have a nice day, sir.   
Police are looking for facts and evidence, not guilt.  That's the court's job, homeboy.