Government Code §511.021

(a) On the death of a prisoner in a county jail, the commission shall appoint a law enforcement agency, other than the local law enforcement agency that operates the county jail, to investigate the death as soon as possible. Except as otherwise provided by Subsection (b), the appointed law enforcement agency shall conduct the investigation. (b) A law enforcement agency appointed by the commission under Subsection (a) may present evidence to the commission that investigating the death would create a conflict of interest that cannot be mitigated by the law enforcement agency. If the commission determines that the conflict of interest cannot be mitigated, the commission shall appoint another law enforcement agency under Subsection (a) to investigate the death. (c) The commission shall adopt any rules necessary relating to the appointment of a law enforcement agency under Subsection (a), including rules relating to cooperation between law enforcement agencies and to procedures for handling evidence.