What are the elements of a crime?

There are generally two elements to a crime; the physical element and the mental element. Crimes will usually have different factors that classify as the physical element and the mental element.Let us say Sally loved her husband very much and they had been married for 20 years, Sally then hears from a friend that her husband had been cheating on her for 15 years of their marriage, Sally confronts her husband and he admits it , he says to her that he has done this because Sally is a terrible cook. Sally who cannot believe her ears goes to bed wakes up a dawn, she draws up a plan to kill her husband, she then takes a knife and walks to the bedroom and stabs her husband saying "that is what you get for cheating on me". He dies. Do you think that Sally has satisfied the physical and the mental element of this crime?The physical element also known as the actus reus is the acting out part of the offence. This is the idea that the defendant actually has to do an act and this act must cause the prohibited consequence. In this case above the prohibited consequence is death. In Sally's case, her taking of the knife, walking to the bedroom and stabbing of her husband was clearly the cause of his death. The physical element of murder is the unlawful killing of a reasonable creature, this has occurred here. Under the mental element also known as the mens rea, there are four levels, the highest being intention(thus for more serious crimes, the defendant would need to have intended that consequence e.g. murder), the next level is recklessness, negligence and then knowledge(which is the lowest level of mens rea), different crimes may require different mental elements. In this case, as intention is the required mental element, Sally clearly shows she intended to harm her husbands as she plans his death, takes action and states her intentions to kill him while she is killing him. However, there are exceptional circumstances and offences where an omission(not doing an act) may suffice for the actus reus e.g. Battery. Another exception is strict liability offences where no mental element is needed for liability, the defendant only needs to be found in certain situations, although the penalty for such offences are not that high.