KANSAS CITY, Mo. — A Roman Catholic bishop was found guilty on Thursday of failing to report suspected child abuse, becoming the first American bishop in the decades-long sexual abuse scandal to be convicted of shielding a pedophile priest.

In a hastily announced bench trial that lasted a little over an hour, a judge found the bishop, Robert W. Finn, guilty on one misdemeanor charge and not guilty on a second charge, for failing to report a priest who had taken hundreds of pornographic pictures of young girls. The counts each carried a maximum penalty of one year in jail and a $1,000 fine, but Bishop Finn was sentenced to two years of court-supervised probation.

The verdict is a watershed moment in the priest sexual abuse scandal that has plagued the church since the 1980s. Bishops have been eager to turn the page on this era and have put in place extensive abuse prevention policies, which include reporting suspected abusers to law enforcement authorities. But the Kansas City case has served as a wake-up call to Catholics that the policies cannot be effective if the bishops do not follow them.

It was an abrupt ending to a case that has consumed the church in Kansas City and threatened to turn into a sensational, first-ever trial of a sitting prelate. The case had been scheduled for a jury trial later this month, but on Wednesday the prosecution said it would be decided in one afternoon by Judge John M. Torrence in Jackson County Circuit Court.