How do they know what he Googled?

A Briton accused of murdering his American wife and baby daughter made an Internet search on 'how to kill with a knife' just six days before their bodies were found, a US court heard Tuesday.

How do they know this? Where are searches stored on my computer?

www.breitbart.com...

I believe it's called a "Ghost image" That is left behind on the monitor when a user makes an input onto the screen, just like every single letter of this post.

I'm not totally sure about this, i wasn't around (i.e; somewhere i shouldn't have been) when they did I.T forensics while i was studying it.

Or you go to internet history. It usually is defaulted to save everything for 7 days. And even then, once the police seize it, they can look at anything ever done on the computer