Any document under these rules which is filed pro se by an inmate who is confined in a penal institution and who is a party in either a civil or criminal case is timely filed if that document is deposited in the institution's internal mail system on or before the last day allowed for filing by these rules or by court order. If an institution has a system designed for legal mail, the inmate must use that system to receive the benefit of this rule. Timely filing shall be shown by a written certification appended to the document that the document was so filed or the appearance on the inmate mailing of a stamp indicating the date of its receipt by the institution's mail system.
Wyo. R. Prac. & P. 14.04