Mo. Rev. Stat. § 58.300: Coroner to administer an oath to the jurors.

The coroner shall administer an oath or affirmation to the jurors, in the following form:

You solemnly swear (or affirm) that you will diligently inquire and true presentment make, how and by whom the person who here lies dead came to his death, and you shall deliver to me, coroner of this county, a true inquest thereof, according to such evidence as shall be laid before you and according to your knowledge.