Medical conditions, deafness, difficult sitting for long periods, people who know the defendant or officers, people who've been victims of crimes, financial hardship, and more will be excused. Depending on the county, they might call 100 people to select just 12.
If summoned to jury duty in Manhattan, your service may be as long as 2 weeks, from the first day you report to the courthouse. If summoned to jury duty in White Plains, you will be on call for approximately one month.