Background: One morning a couple of years ago, Dymond was in her yard, resetting a circuit breaker at the request of her mother. Four plainclothes Galveston police officers were driving by in an unmarked van, responding to a call that three white prostitutes were working Milburn's neighborhood. The police spotted Dymond (who is black), jumped out of the van and announced that she was under arrest for prostitution. Dymond grabbed a tree and called for her father. The police officers allegedly beat Dymond so badly that she had to be hospitalized (for black eyes as well as throat and ear drum injuries).
Three weeks later, police showed up at Milburn's school and arrested her for assault. Hence, the trial against her.
Here's a previous post on Boing Boing with more information, including links to court documents and other articles.
For the life of me I don't understand why the national media hasn't jumped all over this story.