Fixed it for you.
Sadly, the days when we just naively assumed suspects were lying in cases like this are long gone.
It is an interpretive analysis, most usually, at best, although if it is a Glock handgun (as one person here has said) then some of those do have rather unique barrel characteristics. The things is, all Glocks of that same model would share those same characteristics, but quite possibly not leave markings on projectiles which would result in projectiles fired from those highly similar weapons being distinguishable from one another, most particularly after those had penetrated steel or possibly even glass.
I'm not at all sure they arrested the "right" guy, although others have been arrested too, which on the news were called 'cop-cats'. (one of which was said to have used a slingshot)
I could be wrong about the doubts I'm having that they have the right guy, but I do not want to see an innocent man convicted and so will need to see a whole lot more than what has been revealed so far in order to change my mind.
All the police have(?) is a weapon that they found in a pawn shop, and did some sort of "ballistics testing" with, which led then to conclude that was the weapon that was used?
They'll be needing a lot more than that, if they don't insist upon railroading the guy based on flimsy evidence, coupled with well shepherded, circumstantial evidence bolstered by vociferous accusations on the part of prosecutors of how "sure" they, the prosecutors are (and you, the jury should be sure too -- just look how assertive the prosecution is!)
The results of crime labs are often dubious, while the "experts" employed as prosecutorial witnesses, and what they testify as being the science of the matter, are not exactly on par with the dna lab witness Robin Cotton (OJ trial dna expert witness).
WASHINGTON -- A congressionally mandated report from the National Research Council finds serious deficiencies in the nation's forensic science system and calls for major reforms and new research. Rigorous and mandatory certification programs for forensic scientists are currently lacking, the report says, as are strong standards and protocols for analyzing and reporting on evidence. And there is a dearth of peer-reviewed, published studies establishing the scientific bases and reliability of many forensic methods. Moreover, many forensic science labs are underfunded, understaffed, and have no effective oversight.Forensic evidence is often offered in criminal prosecutions and civil litigation to support conclusions about individualization -- in other words, to "match" a piece of evidence to a particular person, weapon, or other source. But with the exception of nuclear DNA analysis, the report says, no forensic method has been rigorously shown able to consistently, and with a high degree of certainty, demonstrate a connection between evidence and a specific individual or source. Non-DNA forensic disciplines have important roles, but many need substantial research to validate basic premises and techniques, assess limitations, and discern the sources and magnitude of error, said the committee that wrote the report. Even methods that are too imprecise to identify a specific individual can provide valuable information and help narrow the range of possible suspects or sources.