He performed autopsies on many celebrities, including John Belushi, Albert Dekker, William Holden, David Janssen, Janis Joplin, Robert F. Kennedy, Harris Glen Milstead, Marilyn Monroe, Gia Scala, Inger Stevens, Sharon Tate, and Natalie Wood.

He then served a second internship at Orange County General Hospital and a series of residencies at Loma Linda University School of Medicine, and Barlow Sanatorium in Los Angeles.

[2] Noguchi began working in the office of the Chief Medical Examiner-Coroner for the County of Los Angeles (CME) in 1961, and came to public attention after performing the autopsy of Marilyn Monroe.

[3] As new CME, he succeeded his mentor Theodore Curphey and supervised autopsies on a range of celebrities and public figures that included John Belushi, Albert Dekker, William Holden, David Janssen, Janis Joplin, Gia Scala, Inger Stevens, Sharon Tate, and Natalie Wood.

[3] After a petition drive organized by Los Angeles' Japanese American community, Noguchi was restored to the office of CME.

[3] In his second term, Noguchi was accused of speaking too freely to the media, particularly following the November 1981 deaths of William Holden and Natalie Wood, which, along with his moonlighting and alleged mismanagement – a series of articles in the Los Angeles Times alleged that Noguchi's attention to celebrity deaths was causing problems in the more mundane aspects of the CME office – led to his demotion from coroner to physician specialist in 1982.