A long-retired Aitkin County judge was acquitted by a jury late last week on a trespass charge that accused him of driving a pickup truck from his home near McGregor, Minn., into Savanna State Forest to Bass Lake.

The misdemeanor prosecution against Robert Graff concluded in a three-day trial that hinged on a photograph taken by a mechanical trail camera set up by the Department of Natural Resources.

DNR conservation officer Amber Ladd testified that she believed Graff was the person in a baseball cap caught on camera. Vehicle traffic was illegal at that place in the forest.

Graff, retired from the bench for about 25 years, did not testify. His attorney, Bill Peterson of Bloomington, said the picture “was kind of a blob, or blurry.’’ He argued before the jury that Ladd did not take the picture herself, so her identification of Graff was merely an interpretation.

Graff was not at risk of losing his hunting or fishing privileges, but if convicted he could have been fined three times the value of any trespass.

“We are gratified that the jury concluded that the trail camera photograph did not prove what DNR alleged and that it exonerated Judge Graff,” Peterson said.

The state is barred from appealing, he added.

Bass Lake is a small lake located north of Big Sandy Lake and west of Aitkin Lake in the 238,954-acre Savanna State Forest. The forest touches parts of Aitkin, St. Louis, Carlton and Itasca counties.