Production sound mixer William John Daly, who worked in film and television for 40 years, helping to develop a key innovation in the field and earning credits on projects ranging from Oliver Stone’s “JFK” to Dick Wolf’s “Law and Order” franchise, died in Albuquerque, N.M., on Aug. 23. He was 65.

Daly’s first sound recording stint was on a featurette in London for “Goodbye, Mr. Chips” with d.p. John Alonzo. He next worked in post-production on Brian De Palma’s “Greetings” (1968) and Robert Downey Sr.’s “Putney Swope” (1969). He quickly built a reputation as a talented recordist and mixer and someone who could build or repair just about any piece of equipment, and these skills led to his central role in the development of the first “smart” timecode slates in 1974.

Daly was hired as the location sound coordinator for the “Rumble in the Jungle,” the heavyweight fight between Muhammad Ali and George Foreman in Kinshasa, Zaire, which was preceded by a three-day soul concert featuring B.B. King and James Brown, among others. They wanted to film the concert and fight with multiple cameras but not multiple soundmen and to be able to sync all the cameras with the mixed-down multitrack recording of the band on stage quickly and efficiently, so they needed to be able to visually display the timecode for the camera. At the time, however, there were no portable crystal-controlled clocks. So Daly found and modified a Heuer executive desk clock that had a crystal control and plasma display to DC power and turned it into the first smart slate. He built a series of these which were successfully used in Africa to film what eventually became “When We Were Kings,” the 1996 Oscar winner for best documentary.

Shortly after returning to the States, the director of that film, Leon Gast, asked Daly to help him record the Grateful Dead’s last movie concert using the modified clocks. By using the device on U.S. soil Daly lost the opportunity to register it for a patent. Nevertheless, in a 1998 Filmcrew magazine “Master Series” cover story profile of his career, Daly noted that “that clock was probably the most significant impact I’ve had on the business.”

Daly’s numerous film and TV credits during the 1970s and 1980s included “Hester Street,” much-lauded telepic “Bill” (1981) with Mickey Rooney, “Svengali,” “Grace Quigley,” “The Protector,” “Nine 1/2 Weeks,” “Crocodile Dundee,” “The Bedroom Window,” “Five Corners” and “Rocket Gibraltar.”

In the 1990s, Daly began a long association with producer Dick Wolf’s TV series. He worked on the first two plus seasons of “Law and Order” from 1990-92, the “Law and Order” spinoff movie “Exiled” (1998), more than two seasons of “New York Undercover” (1996-99) and more than seven seasons of “Law and Order: SVU” (1999-2006), mixing 160 episodes.

On the feature side, Daly mixed the Dealey Plaza scenes in Oliver Stone’s “JFK” (1991), as well as “The Saint of Fort Washington,” “Six Degrees of Separation,” Stone’s “Heaven and Earth,” Paul Mazursky’s “Faithful” and “The Best Man” (1999).

Born in the Bronx, Daly mastered several musical instruments as a teenager, including the French horn and accordion. He served four years in the Navy, including as an instructor in a pilot program to use RF communication over global-scale distances. He had intended to pursue musical studies, but after his military service he took a job as an engineer at editing house Floyd L. Peterson Inc., where his skills in the recording studio quickly led to work in film.

Daly was based in New York for four decades but moved to Albuquerque in 2008 to work on the Starz series “Crash” (2008). He then worked on “The Spy Next Door” (2010) before retiring.

Daly is survived by two brothers.