Complex sentence: Because Lou is close to Johnnie, Hendricks asks Lou to persuade him to confess, but it was Lou himself who had given Johnnie the marked $20 bill as a tip after taking it from Elmer.
Split into simpler sentences: Because Lou is close to Johnnie, Hendricks asks Lou to persuade him to confess. But it was Lou who had given Johnnie the marked $20 bill after taking it from Elmer.