Most likely a criminal record needed a reasonable geographical distance before it started to pale and become uninteresting.
他估摸着一份案底需要离得相当远才能不受影响。
英语百科
Geographical distance
Geographical distance is the distance measured along the surface of the earth. The formulae in this article calculate distances between points which are defined by geographical coordinates in terms of latitude and longitude. This distance is an element in solving the second (inverse) geodetic problem.