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.
A reasonable person would realize which part was a mistake: that it's a picture of the serial killer, or that the serial killer died in the 80s?
Suing in Bulgaria is likely to end up nowhere with Bulgaria having the worst courts in the EU (a primary reason not being in Schengen)
There as been an interesting case - Aaron Greenspan vs Google: https://www.huffpost.com/entry/why-google-bothered-to-ap_b_2.... It's a very interesting and even entertaining read.
But damn was it satisfying.
Let's start there first before issuing a lawsuit. You only sue if you can prove damages for defamation. Which, as tepid as most people are on here about patent trolls, I can't imaging taking on google. It's literally like taking on god at this point.