Is there any such thing that could erase or change DNA?

You can definitely get rid of DNA because there are enzymes which the body makes and are found in the environment called DNAase enzymes. This means that they literally eat DNA and cut it up. So you can definitely get rid of DNA. Leaving DNA in the sun can also break it down. Changing DNA is actually very different. Changing happens in all of us due to a process called mutation, in which your DNA accidentally swaps a few of the DNA letters around. These letter swaps usually get fixed by DNA repair machinery within the cell. If it's not, it can sometimes lead to cancer. However, there's not actually a technique in which you can physically change DNA, say, at a crime scene, to implicate somebody. The best way to do that is to literally sprinkle some of their DNA at the scene.