One of the many ways that multiples are very different from singletons is the level of group responsibility to which we're held accountable. If one resident tells off the boss, and the multiple is fired, all the people in the system suffer the consequences of that individual's actions by having lost their income and so on. Thankfully in a normal family situation, if one member of the family is conviced of a crime, they are the only one put in jail*. In this case, if a resident does something illegal, the entire body-system may be thrown in jail. For this reason, it's normal for multiples to come up with a method for enforcing what we call 'house rules' amongst all the headmates. This is one important step on the road to leading a functional life.
The concept of shared responsibility is an exceptionally important legal and moral reality that all multiples must deal with. You can be entirely straightlaced and do everything right, and someone else in your head can screw everything up for you and land you in jail, lose your job, lose your spouse, lose your children, lose your home. Individuals in a multiple have a vested interest in keeping an eye on one another. When house rules are violated, and after dealing with the shared responsibility (natural consequences, apologies, fines, guilt, whatever), often multiples turn to the concept of individual responsibility to discipline the individuals within the system who have put the system at risk, or harmed the system.
Another important point in the concept of shared responsibility is that it makes an impression on the media if multiples are always shown to be attempting to avoid shared responsibility in homicide cases, etc. by trying to blame a specific indivdual in their head for having committed a crime. Multiples have no more "license to kill" than anyone else, and if you are unable to control someone in your head well enough to stop them from murdering someone, there is no reason whatsoever for the legal system to let you walk after-the-fact, because then the miscreant in your head might commit another similar crime while the responsible adults in your head have their collective backs turned. This is a risk no legal entity will take.
(* unless it's drug related, in which case law in the US allows the government to confiscate anything you own, even if you were completely unaware of the crime. This does get used too. -- MRW)