1. Core Legal Answer & Context: In criminal law, the fundamental principle for establishing criminal liability is encapsulated in the maxim 'actus non facit reum nisi mens sit rea,' meaning 'an act does not make a person guilty unless the mind is also guilty.' This requires the presence of two essential elements: actus reus (the guilty act or omission) and mens rea (the guilty mind or culpable mental state). However, merely proving the existence of both elements separately is insufficient. A crucial third requirement is the 'concurrence' or 'contemporaneity' of actus reus and mens rea. This means that the guilty mind must exist at the same time the guilty act is committed, and there must be a causal link between the two.

The principle of concurrence ensures that a person is punished only when their blameworthy state of mind directly motivates or accompanies their blameworthy conduct. If a person has the mens rea at one point but commits the actus reus at a different time without that mens rea, or vice-versa, criminal liability may not attach for the specific offense, unless the act is considered a continuing one or falls under specific exceptions.

2. Relevant Statutes and Sections: While the Indian Penal Code, 1860, does not explicitly state the doctrine of concurrence, it is an inherent and foundational principle of criminal jurisprudence in India. Various sections of the IPC implicitly incorporate mens rea through terms like 'voluntarily,' 'intentionally,' 'knowingly,' 'dishonestly,' or 'fraudulently.' The requirement of concurrence is applied by courts when interpreting these provisions to ensure that the culpable mental state coincides with the physical act.

3. Important Landmark Cases:

• Fagan v. Metropolitan Police Commissioner [1969] 1 QB 439 (English case, highly influential in India): This case is a classic illustration of the concurrence principle, particularly regarding a 'continuing act.' Fagan accidentally drove his car onto a policeman's foot (actus reus without mens rea). When the policeman asked him to move, Fagan refused and switched off the engine, forming the mens rea (intention to cause harm). The court held that the actus reus (the car on the foot) was a continuing act, and when the mens rea (intention to cause harm by not moving) was formed, it coincided with the continuing actus reus, thus establishing assault. This case demonstrates how courts interpret the timing of concurrence.
• Mohan Lal v. State of Rajasthan, AIR 2015 SC 2091: The Supreme Court of India has consistently reiterated the importance of both actus reus and mens rea for criminal liability. While not directly on concurrence, cases like Mohan Lal emphasize that the prosecution must prove the existence of a culpable mental state alongside the physical act. The underlying principle is that the two must be connected in time and purpose for guilt to be established.

4. Clear Conclusion: The doctrine of concurrence is indispensable for a just criminal justice system. It ensures that individuals are held criminally liable only when their blameworthy conduct is accompanied by a blameworthy state of mind at the same time. This prevents the arbitrary imposition of punishment and upholds the principle that criminal intent and criminal act must be inextricably linked for true culpability to arise. Without this concurrence, the mere presence of an act and a mental state, if disconnected, would not suffice to establish criminal responsibility.