Mr Justice Tugendhat will give his decision on the meaning of an allegedly libellous tweet she sent after a Newsnight report that wrongly implicated the Tory peer in child sex abuse allegations.
Earlier this month the judge reserved his decision in the case.
If the judgment goes in Lord McAlpine's favour, there will be another hearing at a later date on the appropriate level of damages, unless the two sides reach a settlement.
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Labour strongholds tended to remain so - apart from a major loss for the party in Dudley.