[1] Merrick was nominated by President Franklin Pierce on December 14, 1855, to a seat on the United States Circuit Court of the District of Columbia vacated by Judge James Dunlop.

[1] He was confirmed by the United States Senate on December 14, 1855, and received his commission the same day.

On October 21, 1861, he was placed under house arrest by General Andrew Porter in relation to a writ for habeas corpus concerning a soldier stationed in Washington, D.C.[2] That same day, President Abraham Lincoln ordered Secretary of State William H. Seward to suspend Merrick's salary.

Circuit Court, with opponents of the bill claiming that it was a stratagem to turn Merrick and his fellow judges out of office.

[3] Senator Henry Wilson claimed that Merrick's heart "sweltered with treason" and that his house had become a hotbed of pro-secessionist sympathizers.

[1] He was confirmed by the United States Senate on March 30, 1886, and received his commission the same day.