Texas Local Government Code - LOC GOV'T § 351.066. Duties in Area Served by Municipal Police

(a) A deputy performing duties in an area served by a municipal police department shall promptly notify the police department of the deputy's receipt and response to a complaint constituting a felony offense and on request shall secure and preserve the scene of the offense for a reasonable time until the arrival of a representative of the municipal police department.

(b) The county and municipal departments shall cooperate in any criminal investigation to the greatest degree practical. However, this section does not prohibit a county or municipal officer from performing any duties that are required of a peace officer.