Legal Definitions - si parcere ei sine suo periculo non potest

The Latin phrase si parcere ei sine suo periculo non potest translates to "if he could not spare him except at his own peril." This principle, originating in Roman law, is a foundational concept in the legal justification of self-defense.

It means that an individual is legally permitted to use force against another person if they are facing an immediate and serious threat to their own life or safety, and they cannot avoid that threat without putting themselves in grave danger. In essence, if the only way to prevent harm to oneself is to use necessary force, then such actions may be considered legally justifiable.

Here are some examples illustrating this principle:

• Example 1: Home Invasion
  Imagine a homeowner who wakes up in the middle of the night to find an armed intruder inside their house. The intruder, upon seeing the homeowner, advances aggressively towards them. Fearing for their life and the safety of their family, the homeowner uses a legally owned firearm to neutralize the threat. In this scenario, the homeowner could not "spare" the intruder (i.e., avoid confronting or using force) without placing themselves and their family in extreme peril. Retreat might have been impossible or too dangerous, making the use of force a necessary act of self-preservation.

• Example 2: Street Assault
  Consider a person walking alone at night who is suddenly ambushed by an assailant demanding their valuables and brandishing a knife. The victim sees no immediate escape route and believes they are in imminent danger of serious injury or death. They fight back, causing injury to the assailant, which allows them to break free and flee to safety. Here, the victim faced an immediate and severe threat. To "spare" the assailant (i.e., not resist or use force) would have meant submitting to the attack and risking grave harm. Their actions were taken because they could not avoid the peril without defending themselves.

• Example 3: Escalating Confrontation
  Picture a situation where two individuals are involved in a heated argument. One person, becoming increasingly aggressive and physically threatening, lunges at the other, attempting to punch them repeatedly. The person being attacked tries to back away but finds themselves cornered against a wall. Realizing they cannot escape and are about to suffer significant injury, they deliver a single, forceful push to create distance, causing the aggressor to stumble and fall, thereby ending the immediate assault. In this instance, the individual being attacked was in a situation where they could not simply "spare" the aggressor (i.e., avoid physical engagement) without suffering substantial harm themselves. Being cornered, their only option to prevent injury was to use a reasonable amount of force to neutralize the immediate threat.