Unless you're wearing your, "I HEART HAIR TRIGGERS!" t-shirt when arrested, why is it even remotely reasonable to expect a prosecutor to be able to discern, let alone make hay out of, the fact that you had modified the trigger of your gun (to some roughly common weight)?
Many years ago the Old Fuff was occasionally called upon to testify as an expert witness about modifications to a firearm that might have a bearing on the case. When this happened it was usually because he was recommended to either a prosecutor or defense attorney. Usually things started when a face-to-face meeting was held between the expert and attorney, during which time the specific issues with the firearm were discussed. It was at this point the attorney gained enough insights from the expert to decide what he/she wanted to do next.
When the case involved a supposed malfunction of the firearm was the alleged cause of the incident rather then a deliberate shooting, attorneys on both sides would be conferring with they're respective experts concerning how each could present testimony or physical evidence to support they're side of the question.
When I was involved I would examine the gun and weigh the trigger pull to determine if it was below factory recommended standard. If it was the attorney could contact the manufacturer and usually get a sworn affidavit to what their exact specifications were. They might or might not request to have an opportunity to examine the evidence themselves.
I would then disassemble the gun and examine each part for signs that they had been modified. When guns leave the factory the internal parts are usually finished (blued, case hardened, plated, etc.) and if someone has "polished" them the lack of any remaining finish is substantial evidence that modification occurred.
Such modifications, in and of themselves, aren't necessarily bad, unless it can be shown that they in some way could have made the arm unexpectedly discharge.
My practice if I found evidence of tampering was to take detailed photographs of the individual parts, and support the images with written text explaining whatever the significance was. After that it was up to the receiving attorney to decide in what direction they wanted to go.
My main point is that an attorney does not (and usually is not) particularly knowledgeable about guns. Al they need is someone who is, bring them up to speed in a given area of the subject.