BREST, France—Prosecutors in the trial of a roadside spectator who caused a huge crash on the first stage of the Tour de France in June called on Thursday for a four-month suspended jail sentence, a lawyer for the riders’ union said. The French woman, who has not been named, sent one cyclist tumbling to the ground, with dozens more falling as they rode into him, in a scene that grabbed global headlines. The woman, who turned herself in some days later, had been holding up a cardboard sign towards a television camera, while facing away from the oncoming cyclists. The court will rule on the case on Dec. 9, lawyer Romuald Palao, who represents the Professional Cyclists’ Association (CPA), which is party to the trial, told reporters after a hearing in the French city of Brest. “What we want from this trial is that it helps ensure this does not …