The average tenure of a Supreme Court justice, who are appointed for life, is nearly 17 years, according to a Pew Research Center analysis. Biographical data from 104 former justices found that those who were younger than 45 when they took the oath of office served an average of 21.6 years — nearly a decade longer than those who were sworn in at ages 60 and older.
The longest serving Supreme Court justice is Chief Justice John Marshall, who served for 34 years, 5 months, and 11 days from 1801 to 1835. He was 46 years old when he was sworn in. The current justice with the most tenure is Justice Clarence Thomas, who was appointed nearly 28 years ago, in 1991.
Fourteen of the 104 former justices studied were under 45 years old when they were sworn in and half served for 30 or more years.
The Supreme Court began its latest session on Oct. 7. Among the cases the court is taking up this term are: whether federal law protects LGBTQ employees from discrimination in the worklace; whether ending the Deferred Action for Childhood Arrivals, or DACA, was lawful; a case on abortion resrictions; and a gun ownership case.