This episode reminded me of the three-parter that started off Season 3 as well. After Mom (Katey Sagal) confesses to the murder and Alan throws enough reasonable doubt to get the son an acquittal, mom & son are left in the witness room and immediately start playing tonsil hockey.BTW, this is an old "LA LAW" plot (and undoubtedly other show before that)--but there I think it was two parents who killed their kid. They created sufficient reasonable doubt for each by blaming the other. The tell was that, as they left in the elevator seemingly still blaming each other even after this possibility was raised, they reached out and held hands just as the elevator doors closed.
Same "reaching out and holding hands" to show collusion.
Oh, yeah, that was SO gross...

Nice sig, by the way, Biggles. Always good to see Groucho get his due.