CENTENNIAL — A bullet leaves the barrel of a Smith & Wesson M&P 15 traveling at 3,000 feet per second, covering the space of a large room seven times faster than a human can react.

Five spiraling grooves inside the rifle’s barrel spin the bullet clockwise to improve accuracy. And, when the bullet strikes a person, it causes what Colorado Bureau of Investigation agent Dale Higashi on Wednesday called a “snowstorm effect,” breaking into hundreds of little flakes.

“The damage it causes to the target, the damage it causes to the bullet itself, is dramatic,” Higashi said.

On Tuesday and Wednesday, testimony in Arapahoe County District Court told the microscopic story of the Aurora movie theater shooting.

Three evidence analysts described in tedious detail their scientific analysis of bullet fragments, pieces of metal and gunshot-residue swabs. On Wednesday, Higashi testified that, out of the 150 bullets, shell casings and fragments he looked at, all of the items he could trace linked back to one of three guns — including the Smith & Wesson rifle — investigators say James Holmes used inside the theater in July 2012.

The object of the hearing, for prosecutors, was to show the analysts are sufficiently knowledgable and their methods sufficiently reliable to allow the analysts to testify as specially designated expert witnesses at trial.

Such a designation allows a witness not only to make observations but also to offer an opinion on their significance — and also perhaps gives the witness a little added weight with the jury.

But expert testimony on physical evidence is not expected to play a major role in the trial, which will probably focus more on why Holmes committed the shooting than whether he did. Holmes has pleaded not guilty by reason of insanity, meaning psychiatric exams — like the second court-ordered one scheduled to begin soon — will play a much bigger part.

Still, the defense vigorously questioned the prosecution’s proposed experts this week, seeking to discredit their testimony.

Denver attorney and legal analyst Dan Recht said the defense is continuing with its leave-no-stone-unturned approach.

“You never know what’s going to develop,” Recht said. “You never know how a motion’s hearing is going to change the nature of the evidence being presented.”

Judge Carlos Samour will rule on the experts’ qualifications at a later date.

The next hearing in the case is set for Aug. 25, when both sides will debate the merits of fingerprint identification. The report from the second sanity exam is due in October, and attorneys will have a final pre-trial hearing in November before trial is scheduled to start in December.

Nodding toward the case’s approaching endgame, Samour sent the attorneys off from Wednesday’s hearing with these words: “Use the time wisely.”

John Ingold: 303-954-1068, jingold@denverpost.com or twitter.com/johningold