The Little Falls man who shot two teenage intruders on Thanksgiving Day six years ago should be freed from prison because of an error that briefly closed his trial from the public, his attorneys argued in a federal appeal filed this week.

Byron Smith, convicted of first-degree murder in the deaths of cousins Nicholas Brady, 17, and Haile Kifer, 18, is serving life in a Minnesota prison without the possibility of release. The case drew national attention amid debate over how far a homeowner can go to defend himself and his property.

Prosecutors argued that Smith, whose home had previously been burglarized, sat armed and waiting in his basement and coldly executed Kifer and Brady as they descended his stairs about 10 minutes apart, continuing to fire after they no longer posed a threat. Smith claimed he was defending himself and was fearful after having guns stolen in prior burglaries.

Smith tried to introduce evidence that Brady had been involved in the earlier burglaries and sought testimony from two of Brady’s friends who also were allegedly involved.

Morrison County Judge Douglas Anderson issued an order saying that Smith could introduce evidence of earlier burglaries through law enforcement testimony, but he barred Smith from introducing evidence of Brady’s involvement. There was no evidence that Smith knew who Brady was or believed that it was Brady who had burglarized his home before, the judge found.

The morning the trial was set to open in April 2014, Anderson closed the courtroom briefly to explain the scope of his earlier ruling, including that there should be no public mention of the names of Brady’s friends who allegedly had been involved with him in earlier burglaries. He said he had excluded the public and the media because he didn’t want those names made public.

The Minnesota Supreme Court ruled that the closure was an administrative proceeding to which the public-trial right does not apply.

But while U.S. District Judge John Tunheim declined to overturn the case on federal appeal, he expressed some misgivings about the purpose of the closure and wrote of concern about what he called the trend in Minnesota “toward more restrictions and closures — irrespective of whether they are classified as true, total, partial or otherwise. Indeed, members of the Minnesota Supreme Court themselves have criticized this ‘creeping courtroom closure.’ ”

In a filing with the Eighth U.S. Circuit Court of Appeals this week, Smith’s attorney, Steven Meshbesher, pointed to Tunheim’s ruling and wrote that the courtroom closure requires reversal of Smith’s conviction.

“There is no other adequate remedy,” Meshbesher wrote, adding later: “The right to a public trial is one of the most conspicuous features of American justice … it is incumbent upon the courts to jealously guard against any trespass upon such an important right.”