Bill Tilghman's first documented service as a lawman began on January 1, 1878, when he became a deputy under Sheriff Bat Masterson. Within a month of his appointment, Tilghman was charged with being an accessory to an attempted train robbery. On February 12, the charges against him were dropped for lack of evidence. Tilghman was again suspected of a crime two months later, on April 16, when he was arrested by Masterson on a charge of horse theft. Once again the charges were dismissed. Troubles of a different sort came up on March 8, 1879, when Masterson had to sell his deputy's Dodge City house at auction, apparently to satisfy a judgment.