A guilty deed or a wrongful act. (Physical act in commencement of a crime).
If there is any act or omission which results in wrongful loss or gain of any person or causes grievous hurt or injury to any person then such acts amounts to actus reus(culpable action). In other words without a guilty act there can be no crime. Actus Reus can also be the omission of any act. If any person is legally bound to do certain act s and he or she wilfully neglects it knowing that such omission will cause loos or damage to certain persons then such omissions also amounts to actus reus.
Actus Reus is the physical elements of a crime. For a conviction under criminal law an act or omission must be committed. The fundamental idea behind this maxim is that no one can be punished solely because of their criminal thoughts or intentions. Criminal thoughts does not cause any harm to the society until and unless it is accompanied with an act or omission. The actual physical act in pursuance of the intention is what makes the person liable of a crime. Thus Actus Reus needs to be established to prove guilt of the accused and whether the crime had been committed or not.
If a person carries a knife to another person’s house and repeatedly stabs the person then the act of carrying the knife and stabbing are both actus reus.
It is the duty of the nurses to take care of the patients and provide them with proper medicines on time. If any nurse fails to provide the proper medicine to a patient and it turns out to be fatal then such omissions amounts to actus reus.
In the case of R v White the defendant put potassium cyanide into a drink for his mother with intent to murder her. She however died due to a heart attack. But her sons action of placing the potassium cyanide in her drink amounts to actus reus.
In R v Jordanthe victim suffered severe stab wounds and was subsequently admitted into the hospital. The victim died after 8 days. His wounds were healed but he lost his life due to medical negligence. Thus the omission on the part of the hospital is also actue reus.
Further in the case of R v. Miller it was observed that when any person creates a dangerous situation which will cause harm to others then it is the responsibility of that person to create a save environment for others. If such act is omitted then it will be held liable.
Edited by Vigneshwar Ramasubramania
Approved & Published – Sakshi Raje
 R V. White,  2 KB 124
 R V. Miller,  2 AC 161