From the court rules regarding RULE IRLJ 3.1
:

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Neither party is precluded from investigating the case, and neither party shall impede another party's investigation.
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Also knowing that discovery is limited (very limited).

Can a defendant demand that the officer be made available to answer questions (not being compelled to be under oath)? Ex: a deposition is a questioning under oath; an investigation may include asking ? not under oath.

And I would think that the investigation can be tape recorded??

From my reading of the WA court rule, a defendant can perform an investigation ... which may include: sitting in on morning briefings of the police station shift changes (see if they have quotas); forcing the officer to answer questions ; examining the SMD & actually testing the machine ; reviewing & obtaining copies of any manuals of the SMD, copies of the officer's training records, etc.

I would think that the court rule, which was designed to screw the defendant, may actually be used to the defendant's advantage.

I have not seen any court opinions that would suggest that a defendant cannot do these types of investigations.

And a violation of the court rules (ie the prosecution tells you that you cannot question the officer, or other investigative activities) would likely be grounds for dismissal.

And an investigation can be broader than discovery (which has actual rules)

Any thoughts from your folks in Washington State? Is CA similar?