A Texas grand jury still could charge the trooper who shouted "I will light you up!" during a traffic stop resulting in the arrest of Sandra Bland, a move that would focus attention on what experts say is lax state police handling of complaints and misconduct.

Records provided to The Associated Press show at least six formal complaints found valid since January, 2012 against members of the nearly 4,000-strong state force for violating traffic stop procedures.

But authorities cannot put a number on informal accusations — such as rudeness or attitude — in which citizens don't sign affidavits that trigger formal investigations. Law enforcement watchdogs said that is a departure from most major U.S. police departments.

Bland's arrest and death in jail heightened concern about police treatment of African-Americans.