This appears to be a symbolic reenactment of the murder, providing an opportunity to dramatize the declaration that follows, having it attached to the representation of the crime. The sages interpret the uncultivatable ground and the young, as yet unproductive, calf as focusing attention on the lost potential of a life snuffed out. At this point kohanim come forth. They were not involved earlier perhaps to assure the slaying not be confused with some type of sacrifice. Following the calf slaying, the elders wash their hands and make a declaration.
Washing hands is universally symbolic of cleansing from a crime committed.
It explains the ritual to mean that there is a question of indirect causation. The crime may have come about because a hungry man could not find food or a traveler was allowed to enter a danger zone unescorted. According to the sages, the lack of safe and appropriate community infrastructure, the neglect of providing vital economic and security needs, etc., is viewed by the Torah as causative to crime and is a failing leadership must answer for. Such introspection leads to improvement within the leadership and betterment of society. The declaration of innocence is followed with a prayer beseeching G-d to cleanse Israel from the consequences of having innocent blood shed in its midst.