Defense lawyers are well aware of the unequal treatment given experts presented by the State and those presented by the defense.Although no one will admit it, most defense lawyers have never seen a State expert excluded. While not the subject of this post, the lax scrutiny given State experts is one of the reasons there are so many convictions based on "junk science".
A great example of just how far a court will bend is the recent case of Petriciolet v. State out of Harris County. The state wanted to use testimony from the director of Family Violence Services at the Harris County District Attorney's office, J. Varela. They wanted her to testify about her "lethality assessment" of the defendant. She admitted that she was not aware of whether such assessments had ever been tested, and knew they had a pretty high rate of error. She also admitted that her testimony had been excluded in other courts, and also admitted that her testimony was nothing more than common sense. Despite all of that, the court allowed her to testify.
Fortunately, the Court of Appeals held her testimony was nothing more "junk science", and the State had not shown the subjec of her testimony was a legitimate field of expertise.
While most of the time the testimony isn't this far out there, it shows just how little scrutiny some courts will give the State's expert. Here Ms. Verala did everything but tell the court she shouldn't be testifying as an expert.
For the most part, I have seen courts change their approach to all experts, and make a serious attempt to ensure they are gualified. Such scrutiny is necessary if we are to ensure people are convicted solely on reliable, credible evidence. Unfortunately, there are still the exceptions.