SAN FRANCISCO – April 17, 2026 – Breaking news from the U.S. Attorney’s Office for the Northern District of California indicates that Ken Mattson, a prominent Sonoma Valley investor and developer, is poised to plead guilty to at least one count of wire fraud. The 64-year-old is accused of orchestrating a sprawling Ponzi scheme that allegedly defrauded hundreds of investors out of more than $100 million over 15 years. This development, expected to unfold in a federal courtroom, marks a critical turning point in a case that has sent shockwaves through Northern California’s investment community.
The Charges Against Ken Mattson
Federal prosecutors have laid out a comprehensive case against Ken Mattson, alleging he ran a “classic Ponzi scheme” that began as early as 2009. Mattson is accused of soliciting millions from investors under false pretenses, claiming they were purchasing legitimate interests in limited partnerships that owned real estate. However, these were reportedly “off-books investors” who never held actual stakes in the partnerships. Instead, Mattson allegedly diverted these funds for personal lavish expenses, to acquire and fund properties under his personal entity, KS Mattson Partners LP, and crucially, to pay off earlier investors – a hallmark of a Ponzi scheme. To maintain the elaborate deception, Mattson reportedly furnished investors with fake tax documents and fraudulent distribution payments, a practice that continued until the scheme’s inevitable collapse when new funds could no longer cover existing payouts.
Scale of the Crime
The alleged fraud by Ken Mattson is staggering in its scope. Prosecutors claim over $100 million was siphoned from hundreds of unsuspecting investors. The U.S. Securities and Exchange Commission (SEC), in its civil enforcement action, specifically charged Mattson with operating a $46 million affinity fraud scheme impacting approximately 200 investors. In one instance, Mattson reportedly raised $24 million between 2019 and 2024 for a fund, with at least $10 million of those funds allegedly used to prop up accounts and pay distributions rather than legitimate investments. Furthermore, between 2019 and 2024, Mattson allegedly obtained at least $28 million from investors for “off-books” investments in just two properties, Divi Divi and Heacock Park.
Who Is Ken Mattson?
Kenneth W. Mattson is a 64-year-old American real estate investor and developer, a well-known figure in Sonoma and Northern California. He operated as a registered financial advisor, broker, and tax preparer. Mattson co-founded LeFever Mattson with Tim LeFever, a corporation based in Citrus Heights, California, managing some 50 limited partnerships in real estate. Mattson served as CEO and CFO of LeFever Mattson from 1989 until April 2024, when he resigned following an internal investigation into his conduct. He also launched KS Mattson Partners with his wife, Stacy, which prosecutors allege became a vehicle for personal enrichment through the scheme.
Investigation Details
The unraveling of Mattson’s alleged scheme was a multi-agency effort, spearheaded by the U.S. Attorney’s Office for the Northern District of California, the FBI, and IRS Criminal Investigation (IRS-CI). The SEC also filed a parallel civil enforcement action. The first cracks in Mattson’s façade appeared in late 2023 when his long-time business partner, Tim LeFever, discovered the misconduct. LeFever, whose private journals and letters detailed years of anxiety over Mattson’s financial dealings, reported him to federal authorities in spring 2024. Community concerns also mounted, with local residents forming “Wake Up Sonoma” in 2022 to investigate Mattson’s unusual property acquisitions and vacant holdings. After learning of the SEC investigation in April 2024, Mattson allegedly deleted thousands of relevant files, leading to an obstruction of justice charge.
“This case serves as a stark reminder that even well-established figures in tight-knit communities can exploit trust for personal gain. The alleged scale and duration of this scheme underscore the critical need for due diligence, even when dealing with familiar faces.”
What Happens Next
Ken Mattson, initially charged with seven counts of wire fraud, one count of money laundering, and one count of obstruction of justice, is now expected to formally plead guilty to at least one wire fraud charge. This plea agreement, discussed in an Oakland federal courtroom on April 11, 2026, could lead to a maximum 20-year prison sentence. Prosecutors have until May 8, 2026, to submit a proposed plea order to U.S. District Judge Jon Tigar, who will then decide whether to accept the deal at a hearing scheduled for May 11, 2026. Mattson, who was arrested by the FBI in May 2025 and later released on a $4 million bail with GPS monitoring, faces significant financial restitution, though his remaining assets are complicated by the bankruptcy filings of LeFever Mattson and KS Mattson Partners in late 2024. The SEC is also pursuing permanent injunctions, disgorgement, civil penalties, and an officer-and-director bar.
This case is a sobering reminder for investors. Red flags such as promises of unusually high returns, pressure to invest quickly, or a lack of transparent documentation should always trigger caution. Furthermore, be wary of “off-books” investment opportunities or any scheme that discourages independent verification. Always ensure your investments are recorded and accessible through official, regulated channels, and never hesitate to question inconsistencies, even from trusted advisors.
