Law & Order Season 21 Episode 4 revolves around the strange circumstances surrounding the death of a judge.

When a family court judge is found dead, there is no shortage of suspects. The judge had many enemies, starting with a man who lost a custody case in front of him recently, and also had a gambling problem. Most of these leads result in dead ends, however.

Finally, a hair on the murder weapon leads the cops to Lucy McDaniels, a tennis player who has no apparent motive for the crime. McCoy says that they should try the case anyway and make it clear they don't know the motive but lay out the evidence.

As the case proceeds, Lucy's attorney suddenly files an intention to plead not guilty by reason of insanity and a psychiatrist testifies that Lucy was manic and didn't know right from wrong. Price doesn't buy this, and further investigation reveals that the psychiatrist didn't treat Lucy. Another psychiatrist did, and she was fired when she wrote a letter to the judge saying that Lucy was competent and didn't need her father to be her guardian.

After learning this, Marhoun wants to try Lucy for manslaughter instead of murder, but Lucy's father rejects a plea deal.

To find out what happens, watch Law & Order Season 21 Episode 4 online.