The Truth Trap — Frances A. Miller

Winner of the California Young Reader Medal in the high school category and an ALA Best Book of the Year.

Following the death of his parents in a car accident, fifteen-year-old Matt McKendrick runs away from his hometown with his small, deaf sister, Katie, to prevent her from being placed in an institution. Reaching Los Angeles exhausted and hungry, they take refuge in an abandoned theater. When Matt returns to the theater after an unsuccessful day hunting for work, he finds Katie gone and the police waiting to accuse him of murder. Alone in a city of strangers, Matt sets out on a desperate quest -- fighting suspicion, hatred, and his own unbearable remorse and self-doubt -- to prove to himself and to the Homicide detective who despises him that he is who he says he is.
 
The Truth Trap is the first book in the series.