The case of William Maher v. The People requires the prosecution to prove both the intent to kill and circumstances that make the killing murder in order to establish an assault with intent to murder. Malice aforethought is necessary for murder, and the presumption of innocence applies to both intent and act. If a homicide is committed in the heat of passion due to reasonable provocation, it is considered manslaughter rather than murder. The extent of the provocation and the time elapsed are factual questions for the jury.

In this case, evidence of adultery committed by the victim with the defendant's wife shortly before the assault was deemed admissible as it could establish that the assault was committed in a state of passion due to the provocation, which would reduce the charge to manslaughter. The defendant's statement was left to the jury's discretion to determine its credibility.

The state of mind of the offender is always relevant in determining the offense. Self-defense, insanity, and sudden passion can affect the degree of the offense, but each of these circumstances is a state of mind that must be evaluated by the jury. In a murder case, it is important to determine whether the accused acted with deliberation and intelligence, had control over their emotions, or if their reasoning was impaired. These factors are all relevant to determining the state of mind of the offender and must be considered by the jury.

To prove manslaughter, the homicide must have been committed in a sudden transport of passion due to a reasonable provocation, without malice. The amount of time needed to cool down after the provocation is also important. Evidence of information communicated to the accused, such as prior threats against them, may be admissible in cases of malicious prosecution. Adultery can be proven by facts and circumstances, and it is not necessary for the husband to witness the act. Self-defense is justified if the danger was believed to be actual and imminent, even if that belief was mistaken. Evidence that immediately preceded and was directly connected to an assault is admissible as part of the res gestae.

The case involves a prisoner charged with assault with intent to kill and murder, and the defense offered evidence of an adulterous relationship between the victim and the prisoner's wife. The court rejected the evidence, and the main question is whether the proposed evidence would have reduced the charge from murder to manslaughter. To reduce a killing from murder to manslaughter due to passion, reason should be sufficiently disturbed or obscured by passion to the point where ordinary people might act rashly or without due deliberation. The provocation should have a natural tendency to produce a state of mind in ordinary men, but not be so certain to produce such a state of mind that the individual cannot be held morally accountable. The same principles apply to the time during which the continuance of passion may be recognized as a ground for mitigating homicide to manslaughter.

The lower court erred by not presenting certain evidence related to the assault, which could have affected the verdict. This mistake also affected the interpretation of the prisoner's statement. A new trial is necessary. The judge disagrees with the inclusion of evidence related to provocation, but this does not change the decision to order a new trial.