Except for the last two Chapters, most of the rest of the novel is seen through the eyes of Mr. Utterson, who functions as the "eyes" of "conscience" through which we, the readers, evaluate most of the novel.
Therefore, if Utterson is deceived in his opinion of some event, then the reader is likewise deceived. This is because Utterson is such a fine, objective narrator who represents a highly moral and upright person; thus, we believe all that he says, and since he is a man of such prominence and integrity, we cannot doubt his explanation or his view of any event.
Utterson is a strange case of opposites. We first hear that he has a fondness for wine but mortifies himself with gin instead. This, at first, sounds weird for a moral narrator, but then we are told that he is not censorious — that is, he is not anxious to judge and condemn his fellow man. This allows many people of differing degrees to come to him to seek advice, and it allows him to be privy to the secrets of the great and the less great. Yet, he also possesses an intense loyalty to his friends and is constantly concerned for their welfare. This attribute allows him to be deeply distressed over Dr. Jekyll's relationship with Mr. Edward Hyde. That is, Utterson is a shrewd judge of character, and he sees in Edward Hyde an immoral and evil person, and he is deeply concerned for his friend's (Dr. Jekyll's) well-being.
For example, when he is convinced that Edward Hyde has injured Dr. Jekyll, he is quick to take action and break down the door to the laboratory in order to come to his friend's aid.
Utterson is also the type of person who inspires trust — and deservedly so. When his friend Dr. Lanyon leaves a note not to be opened until Dr. Jekyll's death or disappearance, he is tempted to read it in order to see if there is any information which will assist Dr. Jekyll. Yet his honor forces him to store the document away without reading it.
Ultimately, we do not know how Utterson is affected by the revelation found in Dr. Lanyon's and Dr. Jekyll's confessions, but from the horror of seeing Dr. Jekyll at the window, when Dr. Jekyll apparently began changing into Hyde, we can assume that Utterson was deeply affected, but due to his objective control over life and its vicissitudes — as a lawyer he has seen all types of criminals — we can assume that, unlike Dr. Lanyon, Utterson was able to survive.