On Tuesday, federal authorities declared a group of works sold through Knoedler & Co. to be fake and charged dealer, Glafira Rosales, with tax fraud. Rosales failed to disclose $12.5 million that she earned from the sales and hid much of the proceeds in a Spanish bank account. The works, all new to the market were said to be from a collector based in Zurich and Mexico City who Ms. Rosales refused to name, were embraced by Knoedler and sold for millions of dollars. If convicted of all counts, Ms. Rosales could be facing a maximum sentence of 34 years in prison.