* Utterson was a close friend of Sir Danvers Carew: As a respected lawyer and a friend of the deceased, the police considered Utterson a valuable source of information. They hoped he could provide insights into Carew's character, relationships, and any potential enemies who might have had a motive for his murder.
* Utterson knew Mr. Hyde: Utterson was already aware of the mysterious Mr. Hyde, who had been linked to Carew's death by a witness. The police hoped that Utterson, knowing Hyde's identity and his relationship to Dr. Jekyll, could shed light on the circumstances leading to the murder.
* Utterson was a respected figure: Utterson's reputation for honesty and integrity made him a reliable source of information. The police trusted him to cooperate with the investigation and to provide accurate and valuable insights.
The police's contact with Utterson serves as a catalyst for the unfolding of the story, as it forces Utterson to confront the unsettling truth about Mr. Hyde and his connection to Dr. Jekyll.