When he left the position of Solicitor General in 1897 Conrad was retained by President McKinley on behalf of the federal government in Morris v. U.S. In October 1901 he joined the law faculty of Georgetown University as lecturer on the history of English law. In 1904 Conrad was again retained on behalf of the federal government as a special prosecutor in the Postal Fraud Cases. During the last 20 years of his life he was constantly engaged in appeals before the Supreme Court where his outstanding ability had wide scope. He achieved his greatest success in the last case he was engaged on, Commonwealth of Virginia v. State of West Virginia, involving the amount of the contributive share that the latter state should pay toward the public debt of the former. Appearing as counsel for Virginia, Conrad's argument upon demurrer in the Supreme Court (206 U.S. 290) was in professional circles considered remarkable. Judgment was ultimately given against West Virginia for $12,393,929. For this complicated litigation he was specially retained by the bond-holding creditors.

Conrad was of striking appearance, tall of stature with an erect military bearing. Though wielding great political influence in his state, he did not care for public office. By nature somewhat of an aristocrat and reserved in manner, he was never what some might call a "good mixer". As a lawyer he excelled in discussing constitutional questions, and was at his best in appellate work before the Supreme Court. He had an extreme distaste for routine office work. Holmes Conrad was married twice and had seven children. After his death on September 4 1915, he was buried in Mt. Hebron Cemetery, Winchester, VA.