Initially interested in ghost hunting, UFOs and other fringe pursuits, Biddle gradually adopted a scientifically minded approach to the study of a wide range of paranormal phenomena.

[5][6] Biddle started to question his approach to investigations into paranormal phenomena when he attended a 1999 ghost hunting convention in Pennsylvania, where a group was claiming to have encountered a hostile entity the night before at the Gettysburg Civil War battlefield.

His expertise in photography and how optical phenomena generate peculiar images on film attracted the attention of Benjamin Radford, who asked him to write for the Center of Inquiry's newsletter.

[9] With Sharon Hill, Biddle established the Anomalies Research Society, a network of professionals investigating claims of paranormal and anomalous events.

"My goal is to gather enough information that will lead to a solid and honest conclusion that sufficiently explains a mystery," Biddle told Newsweek in 2021.

[1] With David Schumacher and Tim Vickers, he compiled a series of observations on what kind of electromagnetic measurements one can expect to get in a house (one that is presumably not haunted), to serve as control in paranormal investigations.