LANCASTER, Ohio (WCMH) -- A Columbus firefighter has been sentenced to prison after pleading guilty to sex crime charges.  On Monday, Christopher Shaffer pleaded guilty to one charge each of gross sexual imposition and sexual battery, both third-degree felonies, in Fairfield County Common Pleas Court. A judge sentenced Shaffer to three years in prison. He will also be required to register annually as a Tier I sex offender upon his release for 15 years.  Shaffer, 38, of Pickerington, was initially arrested on July 21 and charged with first-degree felony rape. At the time of his arrest, Shaffer was placed on administrative duty with the Columbus Division of Fire.