Earlier the court was told that Rio's injuries were likely to have been caused by "heavy blows" from "punches, kicks, knees and stamping".
Simon Phillips QC, for the prosecution, accused Rigby of "striking Rio with such force as to split his liver in two" at around 4.30pm on April 22 this year.
He said the attack was part of "a sustained and violent attack".
He added: "A wicked attack on a defenceless two-year-old child."
More top news
Influential black figures have joined forces to speak out about a deadly disease that sees black men twice at risk compared to white men.
Frances Cappuccini died just hours after giving birth after a string of hospital "failures" including "inadequate diagnosis and treatment".
Sinn Fein will not be re-nominating a deputy first minister following Martin McGuinness's resignation, making an election highly likely.