however, were i the prosecutor, i'd be tickled, one less thing to confuse a jury with, and raise the spector of reasonable doubt.

the problem with most "experts", of this nature, is the almost total absence of hard science underlying their field. a medical doctor can point to something tangible, a heart for example, not so a "memory expert".

In short, the Judge barred the expert because the situation in issue is substantially different from the factual and scientific bases underlying the proposed expert's expertise.  The witness based the opinions on studies involving eyewitness identification and all the flaws we are familiar with.  This case is not about an eyewitness identifying a person, but rather, the defendant allegedly remembering (or not) what the defendant said or did.  These are apples and oranges.  In the litigation context, no one reasonably expects to allow a neurologist to testify as an expert to orthopedic injuries (except insofar as, perhaps, the messed-up joint is impinging on a nerve).  The proposed expert testimony is just that kind of apples and oranges.

Second, the judge noted holdings in prior cases to the effect that "memory decreasing with time is common knowledge", which vitiates any need for expert testimony.  The "common knowledge" doctrine allows a party to put (an argument relying on) opinion testimony before the jury without need for expert testimony, and states generally that "where something is common knowledge, expert testimony is unnecessary", or even barred.  While I've seen used it mainly as a desperation attempt to save a case where an expert has been barred for rendering a lousy report (though once, a med-mal case I worked used it offensively, where a doctor was being tried for malpractice when the patient was Type B and had gotten two units of Type A, not mixing blood types being held common knowledge at least since a 1945 case), I have no doubt that it can also be used to streamline a case by limiting the impact experts would have on the jury (and its' ability to find facts).

Third, the judge reminds the defense they can use cross-examination to take apart the government's witnesses, citing Fitz highly effective cross as an example of its utility.

Fourth, it turns out some of the studies on which the proposed expert's testimony relied, were scientifically flawed. It is always bad for a proposed expert to find out that there's no science or flawed science underlying the opinions.  Things usually collapse pretty quickly then.  A courtroom is not a debating society, where the relative merits of, say, evolution and intelligent design are bandied about.  It is, as much as is possible when dealing with people and the things they say and do, a place where objective proof and logical support - if not absolute science - are required.

Finally, the 403 probative v. prejudicial balancing puts a final nail in Scooter's appellate argument.  The judge said that, even if the expert' testimony was admissible under 702 and Daubert (which it isn't), it would be unduly prejudicial to a fair trial and take up too much time and be only of marginal relevancy (if any) and is therefore barred under 403.  Scooter won't win this on appeal.  Stated simply, the standards of review will not support Scooter's appeal.  Both the 702 and Daubert issue and the 403 issue are reviewed on an abuse of discretion standard.  This standard means generally that the appellate court will only overturn if the error is palpable, plain and the trial judge got it exactly wrong;  the trial judge gets a lot of deference on these calls.  To win this on appeal, Scooter would have to prevail on proving the trial judge got both the 702 Daubert issue and the 403 issue exactly wrong.  He didn't.

a foundation made of sand isn't a good place to build a house.