(CNN) Bill Cosby's defense lawyer says he is concerned about the entertainer's health following what he described as an "unfair" aggravated indecent assault trial that ended in a mistrial Saturday. Prosecutors said Cosby, 79, drugged and sexually assaulted Andrea Constand, the former director of operations for Temple University's women's basketball team, at his home near Philadelphia in January 2004. Cosby pleaded not guilty to the charges. After more than six days of deliberation in Norristown, Pennsylvania, jurors were unable to come to a unanimous decision beyond a reasonable doubt.