Dear N:

You wrote:
> Which of these sentences implies that the crime was necessarily committed by one person?
> Do 2 or 3 imply that the crime wasn’t committed by one person?
>
> 1-Anyone of us could have committed the crime.
> 2-Everyone of us could have committed the crime.
> 3-All of us could have committed the crime.
>
None really imply how many perpetrators there were. All are simply a reflection of the possibility that one or more of “us” had the motive and opportunity to do it.

Often in such a context #1 and #2 would be written “Any one” or “Every one” since “One of us” in most cases is the subject. Some authorities insist on writing it this way. Others make a distinction with #2 saying that “everyone
of us” is the same as “all of us” while “every one of us” is the same as “each one of us.”

The meaning of the subjects would change if the verb were not conditional. If the verb were not conditional, #1 would probably not make any sense unless you made “anyone” into “any one.” #2 and #3 would mean the same
thing, whether or not “everyone” were divided.

#1 Any one of us committed the crime. (The suspect or perpetrator is in our group. A common situation in mystery dramas. Though more commonly the “any “would be dropped.)

#2 Everyone of us (or “every one of us”) committed the crime. (We all did it.)

#3 All of us committed the crime. (We all did it.)