Jay Justice became enthralled with mushrooms and fungi while pursuing a graduate degree many years ago. After completing his graduate degree, Jay joined the North American Mycological Association (NAMA) in 1980. In 1982, he was instrumental in forming the Arkansas Mycological Society and participated in his first NAMA foray in 1985. He has been a prominent member of NAMA, and a well-known mycologist in the decades since.

In 2011, Justice was the recipient of the Gary Lincoff Award for Contributions to Amateur Mycology, an award that is given each year by NAMA to recognize service performed by selected amateur or professional mycologists.

He has been listed as a co-author on several research papers in mycological journals and he serves as one of the chief mycologists for the Missouri Mycological Society as well as a scientific advisor for the Arkansas Mycological Society, the Cumberland Mycological Society, and the Gulf States Mycological Society. Jay continues to serve as a lecturer and mushroom foray leader for mycological societies and mushroom clubs, particularly in the Southeast.

He has recently co-authored the book Amanitas in North America, which was published in June of 2020.