BISMARCK, N.D. (AP) — A judge in North Dakota has dismissed a felony conspiracy charge against a South Dakota man who prosecutors say was part of the 2016 riot at the Dakota Access pipeline construction site.

Lawrence Malcolm Jr. was charged last year with conspiring to commit criminal mischief based on DNA from a cigarette butt left at the scene. His DNA was on file from a previous arrest.

His attorney, Bruce Nestor, argued that it was impossible to determine where the cigarette butt originated or how long it may have been there.

South Central District Judge Bruce Romanick on Monday signed an order dismissing a charge of felony conspiracy to commit criminal mischief against Sisseton, the Bismarck Tribune reported.

Romanick said the state failed to provide evidence that Malcolm entered into an agreement to commit a criminal offense, which is necessary to support a conspiracy charge. The state has shown that the defendant was there and nothing more, the judge said in his order.

Malcolm still faces a misdemeanor charge of engaging in a riot. If convicted, he could be sentenced to a year behind bars and fined $3,000. Trial is set for Jan. 29.

An affidavit says more than 100 demonstrators halted construction and vandalized equipment during the protest on the Standing Rock Indian Reservation.