Pieter L. de Haseth died on December 22, 2025, at the age of 79. He is survived by his wife of 30 years, Josephine (Jo) de Haseth; his daughter, Catarina (Katie) Campbell; and his son, Stefan de Haseth, both from his prior marriage to the late Kristine Campbell. He was a loving stepfather to Jo’s son, Michael Coxon, and a devoted Opa to his seven grandchildren.

Pieter was predeceased by his parents, Pieter Lourens de Haseth and Jane Debrot, and by his brother, Michiel de Haseth. Pieter is also survived by his half-brother, Stephen de Haseth, who lives in Amsterdam, as well as his half-siblings on his mother’s side in the United States: Jean Fleming, Ray Halpern, Minnie Halpern, and Will Halpern.

Born in Amsterdam while his father was attending law school, Pieter came from a family with deep roots on the island of Curaçao where he spent his childhood. Pieter and his brother Michiel were raised by their father and were especially cared for by their great-aunts Anna Maria and Catarina. At age 13, Pieter left Curaçao for the Netherlands when his father was appointed to represent Curaçao in The Hague. He attended both college and graduate school at Leiden University. In 1970, Pieter moved to the United States to pursue his PhD in Molecular Biology at the University of Wisconsin. Following postdoctoral fellowships at The University of Illinois and the University of Colorado Boulder, he joined the faculty at Case Western Reserve University, where he rose to the rank of full professor. Over a 33-year career, he taught biochemistry and ran a research laboratory focused on RNA polymerase. He retired from Case Western Reserve University in 2015.

Fishing was a lifelong passion for Pieter, beginning with trips in the waters around Curaçao with his uncle Dada. He later shared that love of fishing with his son Stefan on Lake Erie and in the Boundary Waters of Minnesota. Pieter was also a highly accomplished chess player, competing in tournaments across the country and continuing to play online until January 2025.

Pieter will be remembered by family and friends for his sense of humor, his memorable stories, his commitment to teach the next generation of scientists and physicians, and the deep dedication he showed to those he loved.

Donations in Pieter’s memory may be made to the Cornell Lab of Ornithology, 159 Sapsucker Woods Rd. Ithaca, NY 14850.

Family and friends may call at BROWN-FORWARD, 17022 CHAGRIN BLVD, SHAKER HEIGHTS, OH on Friday, January 16th from 5:00-7:00 PM.

A funeral service will be held at Lake View Cemetery Mausoleum, 12316 Euclid Avenue, Cleveland, OH 44106, on Saturday, January 17th at 10:30 am.