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Doctor Horning is a Terra Nationalist officer with both a medical and, evidently, a technological doctorate.
After Apollo was arrested by Brace, Horning is tasked with examining "Charlie Watts" and the equipment on Apollo's person. He pronounces Apollo fit and tries to make sense of the Colonial equipment.
He is later confused by Starbuck's queries for Apollo while listening through Apollo's communicator. This equipment is subsequently retrieved by both Colonial Warriors from Horning's examination room (Experiment in Terra).