Metz was born in Germany on Terra, and enrolled at Starfleet Academy, training as a medical officer. He became a prodigy in the field of medicine, and published a number of papers that were landmarks in their respective fields, all before he'd graduated as a Doctor of Medicine (MD).
However, as a young man (some time before age 26), Metz had become an Adrenalane addict, using the powerful stimulant despite his natural intelligence and talent. He failed three promotion examinations without explanation – in fact, he'd taken each tests while his most recent shot of Adrenalane was wearing off, leaving him impaired. Thus for sixteen long years he never progressed beyond the rank of lieutenant.
Metz was serving on the USS Amundsen, a Galaxy Exploration Command vessel, when his secret drug use was discovered. He was arrested and charged with the use of illegal narcotics, his medical license was revoked, and he was allowed to resign from Starfleet. Afterwards, he spent several years traveling between outlying Federation colonies, making a meager living.
Eventually he came to the Orion worlds, where he met Captain Solomon Kane of the Werewolf, a pirate ship. He signed on as the ship's doctor. Kane ensured Metz's continued employment and loyalty with a steady supply of Adrenalane, which was the only thing he cared about.
In reference stardate 2/1412 (circa 2273), when the Werewolf was on the Orion Colony world of Daros IV, Metz took his Adrenalane injections at The Tears of Rigel, a drug den. If he met any rivals of the Werewolf while in a drug-induced good mood, he would invite them to Mavro's Place for drinks. The Orion bartender there was an old associate of Metz, and would slip the sedative Melanex B into their drinks so Metz could rob them while they were unconscious.
At the time, Hartzer was aged 51. He was 5'11", and was overweight and unfit, with a cherubic face and white hair. He had used Adrenalane habitually, at least once a week and had been using it for over 25 years. On the drug, he was cheerful but completely psychotic, and as he came down, he became a complete idiot. Off the drug, he was bitter, surly and loathed both himself and everybody else. He remained a reasonably competent doctor however, but had no concern for how his patients suffered while he treated them. (FASA RPG module: Orion Ruse)