It is possible to be accused of a crime that someone else did. The defense in cases like this is called "3rd party culpability," or in plain language, "some other dude did it." (SODDI).
Arizona law has been progressively getting better in SODDI cases. The admission of 3rd party culpability evidence is under Rules 401 through 403, Arizona Rules of Evidence, not rule 404(b). (See: State v. Machado) Further, the evidence need only tend to create reasonable doubt that the defendant commited the offense. (See: State v. Gibson).
What this means is if there is someone that you think actually committed the crime, or that you think there is strong evidence against, that could be powerful evidence for reasonable doubt.
Caution is advised, though, because simply presenting an wide variety of possible culprits -- whose connection to the crime is a long shot -- will not suffice.
3rd Party Culpability evidence must be thoroughly flushed out and, if relevant and admissible, presented to the jury.