Howard Martin qualified as a doctor in 1957 and served in the British Army for 18 years. In 1977, he transitioned to general practice, working in Newton Aycliffe, England. His career spanned several decades until concerns arose regarding his medical practices.​

In 2004, following concerns from relatives about the deaths of patients under his care, an investigation was launched into Dr. Martin's practices. He was subsequently charged with the murders of three patients: Harry Gittins (74), Stanley Weldon (74), and Frank Moss (59). The prosecution alleged that he administered excessive doses of painkillers, hastening their deaths. However, in 2005, after a six-week trial, Dr. Martin was acquitted of all charges.

Despite the acquittal, further investigations led the General Medical Council (GMC) to review his conduct. In June 2010, the GMC struck Dr. Martin off the medical register, citing that he had hastened the deaths of 18 patients through the administration of high doses of morphine and diamorphine. The panel described his actions as "despicable and dangerous," highlighting an "autocratic attitude" and a lack of remorse.

In a subsequent interview, Dr. Martin admitted to hastening the deaths of patients, including his terminally ill son, stating he acted out of "Christian compassion" to alleviate suffering. He acknowledged administering fatal doses of painkillers, sometimes without explicit consent, but maintained that his intentions were to provide comfort and dignity to his patients in their final moments. ​

Dr. Howard Martin passed away in April 2024 in County Durham after a short illness.