Maimonides Guide, Book III Chap. XL:
"The beneficial character of the law concerning "the breaking of the neck of a heifer" (Deut. 21:1-9) is evident. For it is the city that is nearest to the slain person that brings the heifer, and in most cases the murderer comes from that place. The elders of the place call upon God as their witness, according to the interpretation of our Sages, that they have always kept the roads in good condition, have protected them, and have directed every one that asked his way; that the person has not been killed because they were careless in these general provisions, and they do not know who has slain him. As a rule the investigation, the procession of the elders, the measuring, and the taking of the heifer, make people talk about it, and by making the event public, the murderer may be found out, and he who knows of him, or has heard of him, or has discovered him by any due, will now name the person that is the murderer. And as soon as a man, or even a woman or handmaid rises up and names a certain person as having committed the murder, the heifer is not killed. It is well known that it is considered great wickedness and guilt on the part of a person who knows the murderer and is silent about him whilst the elders call upon God as witness that they know nothing about the murderer. Even a woman will therefore communicate whatever knowledge she has of him. When the murderer is discovered, the benefit of the law is apparent. If the court of justice cannot sentence him to death, the king may find him guilty, who has the power to sentence to death on circumstantial evidence; and if the king does not put him to death, the avenger of blood may scheme and plan his death, and at last kill him. We have thus shown the use of the law concerning the breaking of the neck of the heifer in discovering the murderer. Force is added to the law by the rule that the place in which the neck of the heifer is broken should never be cultivated or sown. The owner of the land will therefore use all means in his power to search and to find the murderer, in order that the heifer be not killed and his land be not made useless to him."
Jessie Fischbein translated Yonasan ben Uzziel's comments on Deut. 21:8:
"There comes out a swarm of parasitic worms from the inside of the navel of the calf, it draws and goes until the place of the murderer there and piles up on him, and Beis Din captures him and judges him."
On Yonasan ben Uzziel's comments Zev Farber wrote:
"For a metaphoric explanation of this, see the Torah Temima on this chapter n. 67 (he compares this to Rambam's explanation of Eglah Arufah in the Moreh), also the Maharsha Hiddushei aggadot, Sotah 46a. The upshot they offer is that it [the insects emerging from the Egla's navel] is a metaphor for the "gossip" of people which will ensue if one makes a big deal out of the death of this person. The more talk, the better the chance to find the murderer."
It is clear that Yonasan ben Uzziel offers more than mere translation. With this metaphor he elaborates on the Egla's purpose, which agrees with Maimonides. The insects emerge from the Egla's naval. But why from here? Perhaps this mirrors the punishment of the Spies: "…their tongues were extended to their navels and worms exited their tongues and entered their navels (Rashi, Num. 14:37)." The Spies' evil (wormy) speech caused them to forfeit the land, a place of sustenance. The navel too is the source of sustenance and this metaphor conveys that the Spies' speech ruined their own sustenance, i.e., Israel was lost.
But sustenance also correlates with "life." Yonasan ben Uzziel's metaphor suggests that the Egla generates a literal "buzz" concerning matters of life…the victim. The insects' buzz refer to the speech of the townspeople; emerging from the navel – matters of life; and the swarming of the insects towards the murderer's home means the speech will eventually identify the murderer.
Rambam suggest that this talk will help bring about the murderer's identity, and eventually justice. Public events generate talk. People who knew the victim might start a dialogue with others, naming those last seen with the victim or with whom the victim had ill dealings. This will result in the elders and the courts interviewing those named suspects. Alternatively, the talk that builds and spreads throughout the community will cause the murderer to flee, and his sudden absence will reveal his guilt. This explains why is the Egla Arufah is not brought in cases where the assailant is known.
But this law does not guarantee identifying the murderer. We might suggest that another purpose is still served. Had a murder gone without a response from authorities, this might lead to a real concern by the community that their leaders are incapable. "We are at risk" is a very likely sentiment. The elders' testimony acts to also instill confidence in the townspeople and removes any worry that they are without protection.