A New Mexico county commissioner who founded a group called Cowboys for Trump was found guilty by a judge on Tuesday of breaching the US Capitol during the January 6 riot, a second consecutive win at trial for the US Department of Justice.

Following a two-day non-jury trial, the US district judge Trevor McFadden said the defendant, Couy Griffin, was guilty of one of the two misdemeanor offenses.

The ruling bolsters a key theory from prosecutors in hundreds of related cases.

They argued that the Capitol grounds were strictly off-limits on 6 January 2021, and that should have been apparent to the thousands of Donald Trump supporters who breached them in an attempt to stop Congress certifying Joe Biden’s election.

The judge found Griffin guilty of entering a restricted area protected by the US Secret Service but cleared him of disorderly conduct.

McFadden said Griffin should have known not to scale walls and enter the Capitol grounds, but said Griffin was innocent of disorderly conduct because he never tried to rile up the crowd at the Capitol or engage in violence.

McFadden scheduled a June sentencing hearing for Griffin, who faces up to a year behind bars.

Before the mob stormed the Capitol, Trump gave a fiery speech in which he falsely claimed his election defeat was the result of widespread fraud, an assertion rejected by multiple courts, state election officials and members of his own administration.

About 800 people face criminal charges relating to the riot, which sent the then-vice-president, Mike Pence, and members of Congress running for their lives. Some 200 have already pleaded guilty.

Griffin’s bench trial is seen as an important test case as the DoJ attempts to secure convictions of the hundreds of defendants who have not taken plea deals.

The first jury trial for a 6 January defendant ended in a decisive victory for prosecutors earlier this month. After a quick deliberation, a jury unanimously found a Texas man guilty on all five of the felony charges he faced, including bringing a gun onto the Capitol grounds and obstructing an official proceeding.