For libel, you generally have to show harm, but there are some claims that are assumed on their face to be damaging an no proof of harm is needed (libel per-se). Falsely accusing someone of being a serial killer would generally fall into this category.

Edit: I think the harder part would be showing that people would believe the claim (which legally is separate from showing harm). Google could argue that since the box showed the serial killer died in the 80's that a reasonable person would realize it must be a mistake.