He has been a New Mexico resident since childhood and is a graduate of the Albuquerque public school system. After graduating from high school, he served five years on active duty in the United States Air Force, receiving an Honorable Discharge in 1966.

He received his bachelor's degree from the University of Arizona, where he was a member of the intercollegiate debate team and graduated magna cum laude; his law degree from the University of New Mexico, where he was editor-in-chief of the law review, won a position on the national moot court team and graduated first in his class; and a master of laws degree from Georgetown University, where he was selected to be a Prettyman Fellow and was awarded a Certificate of Proficiency in Trial Advocacy.

During his 38 years as a lawyer, Justice Daniels combined frequent classroom teaching, primarily at the UNM School of Law, with an active courtroom practice in a wide range of civil and criminal cases. He has served as chair of the Supreme Court's Evidence and Uniform Jury Instructions committees and as a member of its lawyer Disciplinary Board. He has been honored by the Albuquerque Bar Association with its Outstanding Lawyer of the Year award, by the New Mexico Bar Association with its Quality of Life award, and by the Roscoe Pound Foundation with its National Trial Advocacy Teacher of the Year award. He has been recognized by polls of the legal community with inclusion in every edition of Best Lawyers in America, in the Martindale- Hubbell Bar Register of Pre-Eminent Lawyers, and in Southwest SuperLawyers, among other survey-based publications.

Justice Daniels and his wife, attorney Randi McGinn, have four daughters, three grandsons, three granddaughters and one exchange student from Hong Kong.