After the President’s Council of Advisors on Science and Technology condemned the use of ballistics evidence in courtrooms, Aaron Hernandez’s defense attorneys filed a motion to exclude expert testimony related to ballistics, citing PCAST’s report. The report calls for judges to be better gatekeepers in deciding what kind of evidence should be presented to a jury. If judges permit such testimony, the report says, they should better instruct jurors that the rates of error among firearms examiners are higher than they might expect. One issue with ballistics analysis is that it is a more subjective review by examiners rather than an objective test. Ballistics experts have criticized this report because the council did not have any representatives who were experts in that field.

https://www.bostonglobe.com/metro/2016/10/31/firearms-examinations-forensics-come-under-review/zJnaTjiGxCMuvdStkuSvyO/story.html