Claims that the active ingredient in Round-up causes cancer have been evaluated by multiple agencies, including international agencies, U.S. and foreign regulators, and Monsanto, the product’s manufacturer. CBS News Dot Com says a federal judge in San Francisco will conduct his own review during a set of court hearings that began Monday. There are big stakes for both Monsanto and the groups of people who’ve filed suit against the company. The U.S. District Judge will spend up to a week hearing from experts to help decide whether or not there’s sufficient evidence to support the lawsuits’ claim that exposure to Roundup can cause non-Hodgkin’s lymphoma. The California court will be presiding over more than 300 lawsuits against Monsanto filed by families who are claiming that the company knew about Roundup’s cancer risk and failed to warn them. The plaintiffs will have to convince the judge to listen to their experts. Many other experts have rejected the link between cancer and glyphosate, the active ingredient in Roundup. The court won’t actually determine if there is a connection between cancer and Roundup, but whether the claim has been tested, published, and widely accepted by the scientific community.