Last week’s decision by Circuit Court Judge Karen Ahn to keep secret important court records is a head-scratcher.

Ahn sided with prosecutors in the murder trial of Christopher Deedy, the 28-year-old U.S. State Department special agent who was in town to protect diplomats during APEC and ended up shooting and killing another young man, Kollin Elderts, 23, in some sort of late-night incident in a Waikiki McDonald’s.

The defense wanted a surveillance tape from inside the McDonald’s made public along with a cell phone video taken by a witness and a written motion in which defense attorney Brook Hart lays out why Deedy should be immune from prosecution. Hart contends Deedy was acting in his law enforcement capacity.

But the judge said no. In her written decision sealing the records, she talked at length about the impact on potential jurors who, she speculated, might speculate and misinterpret what happened in the fast-food joint that night.

Ahn, a former television journalist, was particularly worried that the spread of a crime-scene video in today’s Internet culture — we call that going viral — would somehow result in an unfair trial.

Trial is set for September but first there’s another hearing in July and the judge said maybe she’d change her mind and unseal the records at that time rather than wait for jurors to be in the jury box to reveal them.

That doesn’t make sense to us on a number of levels. First, July is much closer to the trial date and you’d think the potential for tainting the jury pool would be just as great if not greater.

Social scientists and legal experts have been studying pre-trial publicity — known in the biz as PTP — for years and studies have concluded that the more a juror sees and hears negative information about a defendant the more likely the juror is to pre-judge and convict. So defense attorneys often seek a change of venue or at least seriously question potential jurors about what they already know as the trial begins.

But in this case it’s the defense that wants the video released. That would suggest it’s favorable to Deedy and that if only people could see it for themselves they might be asking why the county prosecutor is taking this on.

As media attorneys argued in trying to convince Ahn to keep the records open, these kinds of things are not typically kept locked up in a file cabinet in a judge’s office.

Look no further than Florida where the killing of Trayvon Martin by a community-patrol member, George Zimmerman, is getting massive PTP. Not only has a nearly four-minute video of Martin buying Skittles in a nearby 7-Eleven store gone viral, but medical reports, 911 tapes, photos, and myriad other documents and filings are being made public pretty much as soon as they hit the court clerk’s office.

The difference here seems to be it’s the prosecution that is asking for secrecy, not the accused.

This country has a long-standing history and culture of carrying out its legal business in open court and making criminal cases public, with the exception at times of matters involving juveniles and dependency cases.

This is not an episode of Law and Order. Christopher Deedy is facing second-degree murder charges and a lot of years in prison. We think the public ought to have the right to see what the state has on this guy and make up their own minds, including whether Honolulu Prosecuting Attorney Keith Kaneshiro is right to spend the limited public budget he sometimes complains about on a costly murder case.