In what circumstances will a defendant be charged with a criminal charge if he and his codefendants were arrested in the same criminal investigation?

In United States v. Francisco-Romandia, 503 F.2d 1020 (9th Cir. 1974), 31 aliens were discovered in a residence which officers entered with probable cause to believe it was being burglarized. Appellant was not in the house but his codefendants were arrested there. An indictment was returned against appellant, but he was not apprehended until a month later. In the meantime two codefendants stipulated with the government to release all of the alien witnesses except nine. The court held that the "elements of unfairness in Tsutagawa And Mendez-Rodriguez are absent here."