The appointment of "judges and police" mentioned at the beginning of our Parsh, is intended to prevent undesirable events for occurring, such as case of "corpse found in the field," mentioned at the end of the Parsha. Thus, if such an event does occur - even though it occurs in a field, beyond the boundary of their city - it is the "judges" of that city who must perform the service necessary to bring about atonement.

From here we learn that every Jew must take responsibility for his brethren who are lost spiritually "in the fields." Even the great leaders and judges must go out of the city, into the field, in order to share the beauty of Judaism with others.

(Based on Sichas Shabbos Shoftim 5749; Likutei Sichos  vol. 24, p. 131)