The mother of a 7-year- old boy who ran away from a Brooklyn foster home is a drug-addicted, habitual liar incapable of telling the truth about her own kids, a caseworker testified yesterday.

And until Jennifer Rodriguez, 23, provides information about the location of her son, Patrick Alford, she will remain in jail, a Family Court judge said. Investigators say they’ve found no sign of Patrick, who disappeared from a Brooklyn foster home while taking out the trash on Jan. 22.

Cops have not named Rodriguez as a suspect, but Judge Terrence McElrath, believing that she knows where the boy is, is holding the Staten Island woman in contempt of court.