The establishment of cities of refuge marks a profound historical and moral shift from a reality of tribal blood revenge to a structured legal system governed by God's law. This mechanism was designed to restrain the human urge for vengeance, ensuring that anyone who has taken a life receives physical protection until their guilt can be carefully examined.
In ancient times, before formal legal institutions were firmly established, the duty of seeking justice often fell upon the victim's family. The Torah sought to transfer this ultimate authority to the court. However, completely abolishing the institution of blood revenge, especially in cases of accidental killing, might have been viewed as an act of disloyalty by the victim's relatives, potentially sparking even more bloodshed. Therefore, the Torah retained a specific role for the victim's relative, known as the blood avenger, but neutralized the immediate danger by directing the killer to easily accessible cities of refuge [שד״ל]. The refuge system is specifically meant to shield the killer from the fear and wrath of this avenger [רש״י, רבנו בחיי, חזקוני, מזרחי, שפתי חכמים]. Rather than an act of wild, lawless vengeance, the role of the blood avenger is actually a formal legal position. In fact, if a murder victim has no surviving relatives, the court is obligated to appoint a blood avenger on their behalf [רש ר הירש].
The primary approach among commentators is that an absolute legal inquiry is mandatory for any loss of life. Every killer, whether the act was accidental or intentional, must first flee to a city of refuge to secure immediate asylum. Only after reaching safety is the individual brought before the court, which represents the public, to determine whether the appropriate outcome is the death penalty, exile, or a complete exemption [רש ר הירש, ביאור שטיינזלץ, העמק דבר].
The strict prohibition against the killer facing lethal consequences before standing trial operates on two distinct levels. On a basic level, it serves as a direct warning to the blood avenger. Even if circumstances might eventually permit the avenger to strike the killer, he is absolutely forbidden from taking the law into his own hands and carrying out a private execution before a formal trial has taken place [חזקוני, העמק דבר, מלבי״ם, תורה תמימה].
On a deeper legal level, this establishes a far-reaching foundational rule for the justice system itself. Even in a case of absolute certainty, such as if the members of the high court saw the murder with their own eyes, they are strictly forbidden from executing the killer without a proper trial. In such a scenario, the accused must stand trial before a completely different panel of judges. A witness cannot serve as a judge; a judge who personally witnessed a crime is incapable of viewing the accused objectively or actively seeking points in their defense, which is an absolute requirement for a just and fair trial [תורה תמימה, רש ר הירש].