The simple truth is, the defense can't do -shit- right now except try to find a way to convince the judge to either seek that expert testimony or accept a mistrial. They can't aid Rittenhouse's case in anyway at this point so it narrows down to those two 'options'.
They did about as good as they could for the former with their female collogue providing a ton of doubt for the judge... but he then pushed it back till after the jury. They tried filing a motion for mistrial with prejudice and... the judge pushed it back until after the jury. So they tried to compromise, mistrial without prejudice so a new jury could look at it if the prosecution refiled... and the judge pushed it back until after the jury.
The defense did everything they -could-.
Every time the prosecution crossed the line was part of a patently obvious attempt to get a mistrial before they were forced to use their trump card. Any time outside of that they have always firmly toes the line of the judge's patience, only ever pushing again when he was wavering. Rather skillfully at that.
And around them doing that si where I'd center a good portion of my criticism of the defense.
But proactively -doing- it would be a recipe for disaster.
The judge is the worst part of this. He clearly realizes he fucked up with admitting that evidence. The problem for him is that if he admits that there is only one solution, immediate mistrial. And that's gonna be -explosive-. So he's just trying to buy for time and hoping the jury brings back a full aquittal.