The trials took place first at Camp Release near modern-day Montevideo but were moved to the Lower Sioux Agency in one of the few buildings left standing after the war — trader François LaBathe’s summer kitchen cabin.
Sixteen trials were conducted the first day, convicting and sentencing to death 10 prisoners and acquitting another six. During the six weeks that followed, the military court would try 393 cases, convicting 323 and sentencing 303 to death by hanging.
Somewhat more time was spent on the cases in which the charge was the murder or rape of settlers because admissions were much rarer in these cases. After the defendant gave whatever response he cared to make to the charge, prosecution witnesses were called. Where prosecution witnesses contradicted the testimony of the defendant, the commission almost invariably found the prisoner to be guilty.
Following the trials, soldiers moved the prisoners to the temporary Camp Lincoln at Sibley Park in Mankato. Concerned about vigilante justice by angry settlers, the soldiers planned to swing wide of New Ulm on their way to Mankato.
Unbeknownst to the soldiers and their prisoners, the route they chose went near the New Ulm Cemetery located outside of town. As fate would have it, a large group of settlers was at the cemetery on Nov. 9, burying settlers who had had been killed in the region and had been buried in temporary graves or not at all.
When settlers saw the procession in the distance, they rushed to the scene attacking the prisoners with stones, bricks and sticks.
The final decision on whether to go ahead with the planned mass execution of the 303 Dakota and mixed-bloods rested with President Lincoln.
One of the few who didn’t favor a speedy execution was Henry Whipple, the Episcopal bishop of Minnesota. Whipple traveled to Washington to meet with Lincoln and discuss the causes of the war.