Ellie the springer spaniel was tied to the gates of the National Canine Defence League's Darlington Rehoming Centre and left in the freezing cold.
She sat all night until the staff at the centre found her at 7am the next day.
Defence league staff cared for Ellie and, once she was well, she was enrolled on a six-week training course.
She went on to work as a body-scanning drug dog at Buckley Hall Prison, in Rochdale, Lancashire.
Ellie is now a bright and confident dog who does not seem to have been badly affected by the treatment from her former owners.
Her handler, Brian Thornborough, said: "From her early days at the NCDL's Darlington Rehoming Centre, Ellie has truly realised her potential.
"She is excellent at her job, is very happy, lively and has an incredible amount of drive.
"She is also brilliant around people and children. She really is a fantastic dog."
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