This is a common way of announcing a jury's decision in a legal trial. When a jury "finds" that someone is "guilty" of a crime, it means that they have formally decided that the person committed the crime. The jury announces their decision this way:

We, the jury, find the defendant, Jane Doe, to be "guilty" of the charge of first degree murder.

We, the jury, find the defendant to be "not guilty".

The "defendant", by the way, is the person or organization that's been accused of a crime.