Basic Concept  

Law evaluates every crime basis the following:

1. Intention of committing a crime. It signifies the mental state of
2.  the person committing the crime
3. Action by which a criminal act is done, or any unlawful activity is done
4. Sequence of intention and action are to be proved in trial, to punish the offender or convict.

Commission

1. A crime committed by direct action of a person.  
2. Commission arises by enjoining the intent of crime in a valid mental state and consequently the criminal act performed by the person.

Legal Definition  

• When such an act is criminal by reason of its being done with a criminal knowledge or intention, is done by several person, each of the such person who joins the act with such knowledge or intention is liable for the act in same manner as if it were done by individual alone with that same knowledge and intention.
• A series of acts is also considered as a single act of commission of crime.

Example

 Two persons, A and B, agree to murder Y, by giving poison at different times. A & B, give poison according to agreement with intent, to murder Y.

Y dies of the effect of several doses of poison.

Here A & B intentionally cooperates in commission of murder, as each of them does an act by which death is caused. They are both guilty of the offence although their acts were separate.

Omission  

1. Driven by the criminal intent, if a person singularly or jointly with other persons, denies an action which results in an offence or crime, is known as crime by omission,
2. Omission arises by enjoining the criminal intent and denial of action arising from the intent. Here the action is the ‘denial done by the accused’  

Legal Definition  

• When an act is an action of omission committed by a single person or a group of persons, with a criminal knowledge or intention, is known as act of omission. The omission done by group of person acts in same manner as it was done by an individual alone.
• A series of omissions done in an act of crime is considered as a single act of illegal omission.

Example

  A and B are joint jailors in-charge of a prisoner Z, alternatively in a six hour shift. A and B intending to cause the death of Z, knowingly co-operated to omit the supply of food with a criminal intention of starving Z to death. So they both act in their time of attendance, by denying the supply of food to Z. As a result of continued omissions, Z dies of hunger. Both A and B are guilty of murder of Z.

Another situation :

A is the jailor of Z and with intent to kill prisoner Z, continues to starve him, by omitting the supply of food. Z loses his strength and becomes weak, but the starvation caused till now was not sufficient to cause Z’s death.

A was dismissed from office, and B succeeds as jailor of Z.

B without collusion of co-operation with A, continues to starve Z, to cause his death by omission. Z dies of hunger.

B is guilty of murder by omission

As A has neither collaborated nor co-operated with B, is charged with attempt to murder.

Partly by Commission & Partly by Omission   

1. Driven by the criminal intent, if a person singularly or jointly with other persons, does a part of action that stands as commission and part of action that stands as omission, and combines to occurrence of a crime, is known as the crime committed partly by commission and partly by omission.

Legal Definition  

• Whenever the causing of a certain effect or an attempt to cause the effect, by an act or by and omission, is an offence, it is to be understood that the causing of that effect partly by an act and partly by an omission is the same offence.

Example

  A intentionally causes Z’s death by omitting supply of food and partly by beating. A has committed murder.

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