Let's pretend for a moment. Real case scenario
Husband and wife buy a house. Hubby first, wifey second on the mortgage. She's at work. He's home. He goes nuts and kills his next door neighbor when he came over to ask to borrow his power drill.
Is the wife in any way legally responsible? Criminally or in a civil case?
In a civil case, since they are married, she'll lose. No way she walks away untouched.
In a criminal case, if she knew hubby was mentally not all there, knew the gun was there, had reason to suspect 1+1 might = 2 that day, then yes, she can be held criminally liable as well.
Then, keep in mind, its not whether you win or lose the case, its the fact the case will be brought up against you and its expensive to defend.
So, as you said. There is your answer.
Dan