Law enforcement can scour search histories to find clues. You can't stop them, but you can at least stop other people who might come across your data.
Reuters points to cases where thieves got caught by their search history, including one where an art thief Googled the painter’s name to get an estimated value and another where the thief Googled his crime (to see what they were saying about him?) before it was widely reported. They say it’s only going to get worse…
Law enforcement officials, it seems, have pretty easy and routine access to Google’s search-history database, and this is surely only the beginning when it comes to sifting through huge amounts of data to find evidence of crimes. The SEC, for one, has had a large data-mining team in place for a good five years now, going through enormous quantities of data to look for signs of suspicious activity.
As the article points out, private citizens, including journalists, also have access to a wealth of data. While it’s not likely anyone will see the details of your search history without a warrant or court order (unless you leave yourself logged in on a public computer or somebody sneaks on yours) other publicly posted details are available. It’s time to start thinking carefully about what you search for and how you use online public spaces. Even if you don’t commit a crime, the spread of your information can be embarrassing, and damage relationships or job prospects.
Google makes an effort to notify affected users when their information is handed over, but the government can prohibit them from doing so.
You can disable the option for Google to record your search history by clicking the gear icon in the upper right of a search results page and going to Search History. On that page, repeat the process and select Web History and you’ll see an option to turn it off.
To delete what’s already saved, go to https://www.google.com/history.