My mother is a typical Jewish mother. They sent her home from jury duty, she insisted she was guilty.

The humor depends on a double meaning of “guilty.” In a courtroom context, guilt is a legal judgment about a defendant; in everyday speech, it’s a feeling of personal culpability. By having the mother insist “she was guilty” after being sent home, the joke collapses these meanings: the mother internalizes blame so reflexively that she assumes she must be at fault even when she is merely excused from civic duty. The line also satirizes the cultural trope of maternal guilt—how some family dynamics teach children (and parents) to interpret events through self-reproach—while keeping the tone light through exaggeration and misdirection.