Checking your blind spot through the left rear window

I can easily see out my LR window, but - I don’t hang anything on either side. But I don’t turn around to check my blind spot. Trusting mirrors is a weird thing to say. The mirror can’t do anything other than mirror. If you don’t trust yourself using a mirror then that is something to work on. Mine work just fine and I use them and rarely take my attention from the road in front of me while I simultaneously know what is happening on the road behind me.