Scott,
In Gernot Kuehn's book, Views of Los Angeles, he makes the same observation that you have.
Here are scans from the page where he shows a 1912 image of the old courthouse, and a 1978 image of the current foltz criminal courts building
Gernot Kuehn / Views of Los Angeles
Gernot Kuehn / Views of Los Angeles
I did some searches, but have found no discussions as of yet indicating whether the sandstone wall is made from the original court house perimeter retaining wall stones, or if it is made of new stones paying homage to the sites history