At 17, Landis was deeply struck by the loss of his father and he was treated for 18 months in a Kansas hospital, where he was diagnosed with schizophrenic, paranoid, and psychotic disorders and catatonic behavior.

Landis embarked on his journey as an art forger in the mid-1980s, initiating his deceptive practice by presenting several artworks to a museum in California, attributing them to the renowned American 20th Century artist Maynard Dixon and claiming he wished to make a gesture that would please his mother and honor the memory of his father.

During this period, Landis also produced original pieces; some have been sold through Narsad Artworks, which sells work by artists with mental illness.

[3] In 2007, Landis offered his copies of several works to the Oklahoma City Museum of Art, among them a watercolor by Louis Valtat, a harbor scene by Paul Signac, a self-portrait by Marie Laurencin, an oil painting by Stanislas Lépine, and a drawing by Daumier.

In September 2010, Landis went to the Paul and Lulu Hilliard University Art Museum in Lafayette, Louisiana, under the identity of Father Arthur Scott.

But the fact that he did not gain economically from his actions (apart from a few gifts from curators), and that he addressed his donations to specialists who had the expertise to detect his forgeries but did not, protected him in the eyes of the law.

As one art crimes expert put it: "Basically, you have a guy going around the country on his own nickel giving free stuff to museums.

So Leininger and Aaron Cowan, director of the DAAP Galleries at the University of Cincinnati, set up an exhibition to address the general matter of art forgery, and specifically expose Landis's works.

They collected some 60 pieces by Landis, who provided his "Jesuit priest" costume and some of his art books as well as attending the reception as guest of honor.

[18][19] Most recently, Mark Landis' work was the subject of the exhibition "Creative Conscience" in New York City, curated by Wirth Galerie and hosted by Salomon Arts Gallery, and later extended in Luxuny Atelier, a penthouse overlooking Bryant Park.

[38] In 2020 he appeared on the HGTV show Home Town when the makers of the program commissioned a Landis original portrait of a homeowner's dogs to be hung in the historic Laurel house they were restoring.

[39] Landis is the subject of the documentary Art and Craft, directed by Sam Cullman and Jennifer Grausman and co-directed by Mark Becker.