in arizona are there any statutes in regards to allowing or disallowing
  witness testimony from passengers in same vehicle involved in a hit
and run or other type of accident?

Dear einsteinjr-ga; 

Thank you for allowing me to answer your interesting question. Where
the law is concerned that which is not specifically prohibited by law
is presumed to be permissible. In other words, the law is not
specifically designed to establish the millions of things citizens
MUST do, rather the hundreds of things they should REFRAIN from doing.
Having said that, I obviously found no law that says occupants of the
same vehicle CAN be witnesses in the case of a motor vehicle accident
(under certain circumstances), but more importantly I found no Arizona
law that says they cannot. Therefore it is safely presumed to be
permissible.

I scoured the Arizona State Court Rules and found nothing that
prohibited witnesses of the same vehicle from testifying for or
against a defendant or a plaintiff in either Criminal or Civil Court.
In fact, Rule 16 A.R.S. 43(a) broadly and simply defines a witness
this way:

16 A.R.S. Rules of Civil Procedure, Rule 43(a). Definition of witness

?A witness is a person whose declaration under oath or affirmation is
received as evidence for any purpose, whether such declaration is made
on oral examination or by deposition or affidavit.?
http://azrules.westgroup.com/Find/Default.wl?DocName=AZSTRCPR43%28A%29&FindType=W&DB=AZ-TOC-WEB%3BSTAAZTOC&RS=WLW2%2E07&VR=2%2E0

-- Clearly there is absolutely no exclusion of any certain person(s)
in the definition of ?witness?.

17B A.R.S. Traffic Violation Cases Civil Procedure Rules, Rule 18

?All witnesses for the State's case in chief shall be required to
testify prior to the defendant's case. However, a witness not called
to testify in the State's case in chief may be called in rebuttal to
testify to an issue raised by the defense.?
http://azrules.westgroup.com/search/document.wl?RecreatePath=/search/default.wl&n=22&RLT=CLID%5FQRYRLT161498&DB=AZ%2DRULES%2DWEB&Method=WIN&Query=witness&MaxDocs=100&Action=SEARCH&CFID=0&RS=AZR1.0&VR=1.0&RLTDB=CLID%5FDB341398

-- Here again, there is also no exclusion of any certain person(s) in
the rule establishing how ?witnesses? shall be called to testify in
traffic violation cases. In fact, notice that the law also says, ?ALL
WITNESSES for the State's case in chief SHALL BE REQUIRED TO
TESTIFY??. This statement alone appears to exclude no one.

While this forum cannot provide legal advice, I believe what I have
shown you is an excellent example of what a witness is according to
Arizona State law. For the best advice of course you should contact an
attorney or legal professional licensed to practice in Arizona.

I hope you find that my answer exceeds your expectations. If you have
any questions about my research please post a clarification request
prior to rating the answer. Otherwise I welcome your rating and your
final comments and I look forward to working with you again in the
near future. Thank you for bringing your question to us.

Best regards;

Tutuzdad-ga ? Google Answers Researcher


[INFORMATION SOURCES]

ARIZONA STATE COURT RULES
http://azrules.westgroup.com/home/azrules/default.wl

http://azrules.westgroup.com/search/default.wl?DB=AZ-RULES-WEB&RS=WLW2.07&VR=1.0

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I really appreciate your time in researhing information on this     
thank you   tutuzdad