A run of lawsuits and convictions in the United States is showing how easily disputes erupt after the death of an artist or collector, just as the largest intergenerational wealth transfer in history gets under way. In Oregon, John Moody is suing to reverse an estate sale at which dozens of Chinese paintings changed hands for between $45 and $275 each. He believes one of them — an ink scroll of a galloping horse — may be by Xu Beihong, whose works have achieved up to $41.9 million at auction. The complaint does not target the estate-sale company but accuses the buyers of knowingly exploiting the selling agent's failure to appreciate the works' value. Unwinding such sales is difficult in most American jurisdictions, notes Sarah Barker, global co-head of art law at Withers, though courts in places like France can void deals struck under a fundamental mistake. Families often dodge succession planning altogether, she adds — and highly creative people can be the least structured of all. The Oregon case joins a crowded docket. Sentencing was delayed in Canada's long-running Norval Morrisseau forgery trial after allegations that the late artist's estate was complicit in the fakes; in April a Manhattan jury awarded $102 million in damages to the Morgan Art Foundation, Robert Indiana's former agent, in a fight over unauthorised works; and relatives of the photographer Mike Disfarmer settled with the Arkansas Museum of Fine Arts over the copyright of hundreds of posthumous prints amid claims of illegal profiting. Advisers say the sheer volume of material now changing hands is part of the problem. Caroline Sayan of Cadell + Co calls this "the first major generation" of American collectors to die and sell, flooding the market with comparable pieces — while appraisal figures built for tax and insurance are widely mistaken for market values. Technology offers some hope, says Caroline Taylor of Appraisal Bureau, through living inventories and recurring independent valuations, but only if collectors adopt the tools before the estate event rather than after.