The dog in the mug shot is Pep, also known as Inmate C2559. He lived at Eastern State Penitentiary in Pennsylvania beginning in 1924.
Prison folklore says that Governor Gifford Pinchot sentenced Pep to Life Without Parole for killing his wife’s cherished cat. Governor Pinchor said Pep was a mascot for the prisoners. Pep lived among the inmates for about a decade.