Following a brief career in radio, he undertook an analysis of new religions in Switzerland for the Swiss National Science Foundation, funded by a grant; the results of this work were published in a 1993 book, Les nouvelles voies spirituelles.
Following this, he became a lecturer and research associate at the University of Fribourg, and founded the Religioscope Institute and website, which supply information on religion.
Mayer is most well known for his work covering the Order of the Solar Temple, a group notorious for committing several acts of mass murder-suicide in the 1990s, which resulted in a media frenzy.
He has been described by fellow new religious movement scholar George D. Chryssides as the leading authority on the group, and by Info-Secte founder Mike Kropveld as the "foremost expert" on the OTS.
[6] According to French journalist Serge Faubert [fr], at this time, he locally distributed the neo-fascist magazine Défense de l'Occident.
According to the Swiss newspaper La Liberté, Mayer abandoned any political affiliation after returning to Switzerland, and former friends who were members of the Nouvel ordre social stated they no longer had contact with him.
[7] He stated in an interview with L'Hebdo in 1993 that while he did not regret his past experiences, his "approach has changed quite a bit" and he no longer subscribed to any political ideology, and that as to the magazines he had published in, "I'm a free man, I write what I want where I want [...] I don't have to answer to anyone.
[6][2][11] He was on the party's submitted list of five electoral candidates in the 1987 Swiss federal election; at that time he was also vice president of the Association des non-fumeurs (transl.
[9][12] Mayer was a scientific associate of the Bureau d'aide et d'information sur les mouvements religieux (BAIMR), a French-speaking anti-cult organization in Switzerland, founded in 1989.
[17][7] For three years from the late 1980s to the early 1990s, he took part in a program of new religious movement research operated by the SNSF, funded by a national grant of nearly 200,000 Swiss francs.
[16] As a result of this program, he wrote the book Les nouvelles voies spirituelles, described by 24 heures as a "veritable bible" for those wishing to look into cults.
[2] Mayer became much more well known following his investigation into the Order of the Solar Temple, a group notorious for committing several mass murder-suicides; the case resulted in a media frenzy.
[24][25][26] Mayer had studied the organization prior as part of his grant funded study into new religions in Switzerland,[2] and published the only academic writing on the OTS before the violence occurred, Templars for the Age of Aquarius: The Archedia Clubs (1984–1991) and the International Chivalric Order of the Solar Tradition,[15]: 3–4 published in the French newsletter Mouvements Religieux in January 1993.
[6] Blick falsely accused Mayer of having been summoned to court due to a personal connection to the group, which was repeated by the ATS: this was incorrect, and he had actually been invited to assist with the investigation as an expert.
[22][31] He criticized those who fell for conspiracy theories and lies by the leaders of the OTS, as well as members of related religious movements who did not reflect on their beliefs after the deaths.
[34] Mike Kropveld of the cult watching organization Info-Secte, writing for Cultic Studies Review, said Mayer was "considered to be the foremost expert on the Solar Temple".
[3] Following this, he resumed his studies of NRMs and taught at the University of Fribourg from 1999 to 2007, where he was a lecturer and research associate in their comparative science of religions unit.
[36][40] In an encyclopedia entry from 2004, Daren Kemp described the site as being then the "foremost Internet source in French for scholarly information on religion, including NRMs.
[5] Mayer has argued that the increased freedom of speech and criticism that the Internet allows for creates pressure on religious movements for transparency and accountability, particularly with Scientology.
[5] French journalist Serge Faubert [fr], in his 1993 book Une secte au cœur de la République, an investigation of Scientology – whose Office of Special Affairs at the time listed Mayer among those who may be "potential supporters" of the organization, along with other religious specialists like Émile Poulat[6][5] – noted his far-right past, attributing what he viewed as Mayer's "complacency" towards Scientology to it.
[7][6] Mayer, responding to his inclusion in the list, said that he was not a member or sympathizer, and that while he favored neutrality from an academic perspective in more personally involved articles he allowed more criticisms.
[6] Faubert did not mind that Mayer was not leading "a crusade against gurus", but criticized what he perceived as an "allegedly scientific uncritical" tone, and was concerned by his past politics.
[7] At the same time, La Liberté doubted he was still far-right, saying that not even "the best magnifying glass" could detect any right-wing political sympathies in the many newspaper articles he had written.
[48] Three years later he authored Confessions d'un chasseur de sectes, which covers his opinions on his line of work and personal background, as well as how it related to his own religious beliefs.