Gytis Griskevicius, 32, of St Ann's Lane, Boston, denies killing Marina Erte, 33, at her flat in Boston on 20 May 2016.
He is alleged to have beaten her before drowning her with a shower attachment and then setting fire to the flat.
Lincoln Crown Court was told the attack was motivated by jealousy at a new relationship Ms Erte had begun.
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Mr Griskevicius did not give evidence during the two-week trial but denied he was responsible in police interviews played in court.
He admitted visiting Ms Erte's flat on the night she died but said she was "fine" when he left.
Ms Erte's naked and badly beaten body was found in the bath at her flat by firemen who had been called out by neighbours.
Jurors in the trial of a man accused of killing his estranged wife have retired to consider their verdict.