The character Higgins was born sometime in the year 1920. In the episode "Echoes of the Mind" he reveals that he is the second son of the Duke of Perth, a retired senior British Army officer, and Baron of Perth in his own right, though he rarely uses the title. He went to school at Eton College and the Royal Military College, Sandhurst, but was sent down from the latter after another officer cadet allowed him to take the blame for a prank that had resulted in the serious injury of a third cadet. Higgins obeyed an honour code among the cadets by not revealing the true identity of the culprit at the cost of being rejected himself by Sandhurst for an officer's commission. Unable to face his father, he enlisted into the ranks of the West Yorkshire Regiment and he was awarded the Victoria Cross.
Higgins has three half brothers, also portrayed on the show by Hillerman. The first was an American, Elmo Ziller. The second was an Irish priest, Father Paddy McGuinness. The third was Don Luis Mongueo. A fourth named Soo Ling is mentioned but never seen.
The character served for 37 years in the British army in the Second World War, the Indochina War (assisting the French), New Guinea, India and Kenya, among others. Higgins carried the discipline of his military background into his civilian life. He earned the position of sergeant major in the British Army, and was in MI6 the British Secret Intelligence Service.
The character holds a 1947 doctorate in mathematics from University of Cambridge. This is revealed when he tells a pregnant woman (correctly, though misleadingly) that he is "a doctor". He owns two highly trained and intelligent Doberman Pinschers, Zeus and Apollo (whom he often refers to as "The Lads").
Higgins is well versed in both armed and unarmed (kung fu) combat techniques. He expresses fondness for older British Army weaponry such as the Sten and Sterling submachine guns, although he is more than capable of using modern weaponry such as the Heckler & Koch MP5. There is a small collection of weaponry (mostly pistols and shotguns) at the estate that he and Magnum have use of as needed. Occasional episodes show Higgins utilizing less common weapons, such as a 19th-century brass cannon and a samurai sword. Like Magnum, he does not make a habit of carrying a gun.
In regard to his personal life, Higgins was once nearly engaged to be married; years later his old flame visits him in Hawaii. He described her as being built like the Prince Albert Memorial.