"And there fall there" — the Torah describes an animal falling into an uncovered pit. The Mekhilta specifies: this must happen "in the normal mode of falling." The animal must fall in as one would expect — walking forward and dropping into the pit. From this principle, the rabbis derived a series of practical rulings.
If the animal fell before the pit — meaning it stumbled forward in the direction it was walking — because of the sound of digging, the pit-digger is liable. The noise frightened the animal and caused it to fall into the very pit being dug. The digger's activity directly caused the accident.
But if the animal fell behind the pit — moving away from it — because of the sound of digging, the digger is exempt. The animal was moving in the opposite direction of the pit. The fall was not into the pit, and the digger cannot be blamed for an animal retreating from the noise.
However, if the animal fell directly into the pit itself — whether it was approaching from the front or from behind — the digger is liable. The direction of approach is irrelevant once the animal actually ends up in the pit.
These distinctions demonstrate the Mekhilta's insistence on precise causal analysis. Liability requires a direct causal chain between the danger created (the pit) and the harm suffered (the fall). Proximity, direction of movement, and the specific cause of the fall all factor into determining whether the pit-digger bears responsibility.