I trained in a ME setting.

The certification was always first person.Past tense.

This is to certify that I, state your name, performed an autopsy on the body of name and determined the cause of death to be Hirschsptung disease..

Thereafter, it got comical. Third person. "Upon examination of the distal portion of the alimentary tract, this prosecutor found focal necrosis and peritonitis... Or instead of prosecutor , this examiner..

The funny part was the insistence upon the use of the word "decedent."

It was reported by witnesses that the decedent was dancing in the unlit portion of the street... He's a dancing dead person.

I always write in third person. Present tense is appropriate for opinions. Past tense for what you saw.

"the following opinions are held by this writer
"The following criticisms are held by this engineer.


"At the scene, this engineer observed a 12/2 type NN cable with transecting arcing....


All of this is to re emphasize one point. Be consistent report to report.