Where should this Chilean case be tried?

Ministra Romy Rutherford

This one's about Chile. A major investigation has been underway concerning alleged chicanery by now-retired former Army Commander-in-Chief General Humberto Oviedo. The charges relate to embezzlement and travel fraud and involve significant sums. Some of the specifics can be found here.

One issue has concerned the fact that the prosecutor, Ministra Romy Rutherford, is on loan from another court, and that appointment was time-limited. This led to legislation, known as the Rutherford Law, amending the Code of Military Justice to afford her additional time to proceed with the cases. Approval by the Supreme Court was also necessary, and was granted unanimously.

This is not the first time Chile has prosecuted a retired officer in a military court. Is there some reason the charges against General Oviedo cannot be tried in the civilian courts?