He is portrayed by Martin McCreadie.
Sergeant Doyle is a man of Irish descent that lives in New York City. Early in his adulthood, Sergeant Doyle joined the New York City Police Department under Chief Commissioner Thomas Byrnes. He has climbed the ranks of the police, becoming a sergeant and Captain Connor's right-hand man.
Appearance and Personality Edit
Sergeant Doyle is a tall man with a muscular build, short black hair, and light brown eyes. When he does not wear the uniform, he is usually wearing simple outfits consisting of trousers, shirt, vest and jacket and a bowler hat. Sergeant Doyle is a policeman on Paul Kelly's payroll and one of the recruits trained during Thomas Byrnes' mandate as well as the Captain Connor right arm. As such he uses his badge and his uniform as a shield for violent, illicit actions. Openly a racist and a misogynist, Doyle is a corrupt policeman who sees in Roosevelt a threat to his personal gain. Although he is no stranger to the use of violence and abuse of his power, Doyle was still surprised by some extreme acts perpetrated by Captain Connor.
New York City, March 3rd, 1896. Sergent Doyle was stationed at the entrance to the Williamsburg Bridge, preventing entry to the journalists and curious bystanders. The mutilated corpse of a boy-prostitute had been found on the still under construction bridge. When a certain John Moore of the New York Times arrived at the place, Sergeant Doyle barred the passage with his truncheon. The man said he was an illustrator requested by Commissioner Roosevelt; Sergeant Doyle was then forced to let him pass, accompanied by Captain Connor to the scene of the crime.
The following day, Sergeant Doyle showed off his talent for extorting confessions with colleagues along with the former Chief Commissioner Thomas Byrnes and Captain Connor outside the New York City Police Department. A horde of journalists, including Lincoln Steffens was interested in hearing the latest news about Henry Wolff, the man arrested for the murder of the boy-prostitute, identified as Giorgio Santorelli, an Italian immigrant working at the Paresis Hall. 
On April 3rd, 1896, Sergeant Doyle reluctantly took part investiture of new police officers personally picked by Chief Commissioner Theodore Roosevelt to increase the ranks of police officers with young recruits devoid of the influence of former Chief Commissioner Thomas Byrnes.
In the evening, he was in Captain Connor's office counting the bribes obtained through the association with the well-known mobster Paul Kelly, patron of the Paresis Hall among other illegal activities in the Tenderloin. They were interrupted by one of the newly appointed police officers, who informed them of a new murder at Castle Garden. Doyle and Connor looked at each other, coming to the conclusion that Commissioner Roosevelt was trying to keep them unaware of the investigation. Wearing the uniform jackets, they gathered their men and reached the scene of the crime where they found a crowd of nosy journalists outside the building.
Sergeant Doyle backed Captain Connor and former Chief Byrnes, putting Roosevelt in the uncomfortable position of not being able to save any more time for Dr. Kreizler's team that was conducting a parallel investigation. 
Sergeant Doyle was part of the task force that burst into a building when Commissioner Roosevelt discovered that Willem Van Bergen, the scion of a wealthy New York family, was a potential suspect for the murders of Giorgio Santorelli and Ali-ibn Ghazi. However, Connor had managed to manipulate the investigation and mislead the task force to a wrong address. Outside the building, Sergeant Doyle witnessed Commissioner Roosevelt ripping off the badge from Captain Connor's chest, firing him from law enforcement.
After discovering Willem Van Bergen's plans to leave the city in the middle of the Feast of Ascension night, Doyle sought out his former colleague Connor to stop him. The two tracked the young man near the harbor and they chased him over a scaffolding, where Connor shot him in the forehead after several homophobic insults, accusing him of being the murderer they were looking for.
Doyle was surprised by the turn of events, probably expecting they would've arrested Van Bergen after beating him up. Quickly, Doyle wrapped the corpse in a jute sack and the two men threw it into the black water after weighing the body down with stones. 
The next day, Doyle and Connor teamed up to kidnap Dr. Kreizler and his associate, John Moore and bring them to J.P. Morgan's mansion. While the men had a closed-door meeting with J.P. Morgan, Thomas Byrnes and Bishop Potter, Doyle and Connor waited in the courtyard outside.
After Byrnes came out and had a brief conversation with Connor, the latter instructed Doyle to get "The Swede" back and to tell him to bring more chloroform. Doyle nodded and walked towards his car. 
Sergeant Doyle and Connor visited Kreizler House, intending to get rid of the alienist once and for all. Unbeknownst to them, Dr. Kreizler had not yet returned from his trip to Boston, Massachusetts. Doyle and Connor came face to face with Kreizler's housemaid. After repeatedly asking her where they could find the doctor, not knowing that the girl had a speech impairment, Doyle and Connor began to search the house. While Connor went upstairs, Doyle went to the kitchen where he tried to attack Mary, the housemaid. He was going to hurt her but was grabbed by Cyrus, Kreizler's butler who told Mary to run. Before she left the room, she grabbed a kichen knife. Doyle was suffocating due to Cyrus's grip but was saved by "The Swede" who appeared from behind the butler and drugged him with chloroform. Doyle hen rushed wards the stairs just to witness Connor throwing the housemaid off the baluster, breaking her neck in the fall. 
Next day, at the New York City Police Department, Sergeant Doyle was questioned by Detective Sergeants Lucius and Marcus Isaacson about Mary Palmer's death. Doyle was sitting at the table, while Detective Lucius Isaacson stood in front of him and Detective Marcus Isaacson was leaning against the wall.
Sergeant Doyle said that he and Connor were waiting outside the house for the Dr. Kreizler to return when Mary invited them in, asking if they wanted a "lovely cup of tea." Doyle added that he could have told she was interested in more than a cup of tea, so he made himself scarce. Detective Sergeant Lucius Isaacson replied Mary couldn't speak. Realizing that he had just given the detectives the irrefutable proof that he was lying, Doyle tried clutching at straws by stating he wasn't being literal, and that she said it with her eyes. Both detectives were starting to lose their patience, particularly after Doyle claimed that Mary led Connor up to the bedroom by the nose. Detective Lucius Isaacson, then, wanted to know when she fetched the knife. Doyle replied he supposed she had it hidden up her petticoat the whole time.
The shorter of the two detectives lost his temper and asked harshly if he expected them to believe him. Sergent Doyle shrugged, saying that he expected them to believe him "over Sambo and some halfwit stable boy." At that point, Detective Marcus Isaacson snapped and was about to grab Doyle from his shirt, but was promptly stopped by his brother. Doyle laughed at them, saying "Look at yous, a couple of heebs playin' at cops." Unbeknownst to the three of them, Miss Howard had eavesdropped the entire interrogation outside the door. 
- Sergeant Doyle (to Det. Isaacsons): "I expect you to believe me over Sambo and some halfwit stable boy."
- Sergeant Doyle (to Det. Isaacsons): "Look at yous, a couple of heebs playin' at cops."
- — Requiem