Zebo

Yeah, but that can be made plausible though: perhaps he can't get rid of it, as he has (very intrusive) company; or perhaps he thinks he threw it away in a lake, yet it landed on the back of tortoise (joking, but you get the idea). You bring up an interesting point though: bacteria. Imagine the killer throws the knife in a sewer (and the sewer is, via via, connected to the lake). Would bacteria be able to 'eat' the DNA, that is destroy it?

Thanks so far, this is helpful. How about: the victim is stabbed, and the perpetrator keeps the knife for a day. Then he tosses it in a lake, and, two months, later, it washes up on the shore of the lake (or someone finds it at the bottom). Will it still be possible to extract DNA from the knife? (Also, the time span is May/June/July: mid-summer, hot.) (In case anyone's wondering: no, I'm not a serial killer, it's for a student film, a final exam.)

Hi, I hope this is the right forum for this. If not, redirect me please. Imagine someone is stabbed with a knife, and this knife is thrown into a lake. About a week later, the knife washes up on the shore of the lake. A. -- Will it still be possible to extract DNA from this knife (blood, fingerprints)? B. -- And after two months? C. -- If the knife was covered in blood, will that blood still be visible somehow to the bare eye? Thanks in advance.