'Angry Beavers said:
			
		
	
	
		
		
			
	
		
			
				'hamster_13 said:
			
		
	
	
		
		
			Woz, do you know how these experts are picked? Do the defense/prosecution seek out their own people? Or is it more of a case debriefing being faxed to several people and any interested parties respond?
		
		
	 
This. Most experts are just paid whores.
		
 
		
	 
Well, I think that's a bit of an overstatement.  It is correct that each side seeks out their own experts.  And, generally, there are some experts who tend to testify more frequently for the state and defense. That said, all these experts are subject to a particular rule that, essentially, they must be both educationally qualified and are up to date with the literature and commonly accepted issues in the field.  This really makes the "options" pretty limited and for the most part very well known in the criminal defense bar. As to how they are chosen, it really is just lawyers on each side picking them.  Where it may different is in the costs of each expert.  If the lawyer has a private client with deep pockets, they can pick and choose each expert (which is freaking expensive - I had one quote me 500/hr today). If it is a court-appointed attorney case where the defendant has been legally determined to be indigent (which Arias may be), the defense attorney must submit a request either to the judge or to the administration office which handles indigent defense funds.  In those cases, generally the court/office will require some generic reasoning as to why the expert is necessary to put on an effective defense (sometimes this isn't easy) and will usually grant minimal funds.  For example, there are two prevalent DUI "experts" in Arizona that I use.  One costs 5000 and one costs 1500 per case - you can guess which one the court will grant me funds for.
Speaking more to the "whore" comment I do want to stress that it's not like these experts can get up there and say anything.  As I mentioned, they are subject to accepted standards in the area and attorneys are familiar with them.  I know that prosecutors in this state keep a database of notes on certain experts and, if the prosecutor is a good lawyer, will know which questions to ask the expert to elicit answers which actually hurts the defense's case.  Additionally, an experts "opinion" almost always speaks to some generic possibility that may or may not be able to affirmatively be shown in the particular trial case.  Using the DUI example, I can have the expert testify to several factors which 
could cause the breath or blood test machine to give an incorrect result, but it's near impossible to show any of those factors were absolutely present in my case - I just gotta hope the "could be" sounds like reasonable doubt to a juror.