If the data out there is true about various bullshit forensics practices out there, even with a witness you could get off. Police like to rely on witnesses, fingerprints, some try and scare still using the old polygraph but each are easy to manipulate. The first you just need to mold the memories to your need with a witness, cast doubt so they may question what happened and it's not hard if you know what to say to direct that train of thought. Fingerprints while fairly good aren't unique to each person, so there's always a chance you can have a double or more out there and there have been a few cases where the wrong dude was busted over a fingerprint on a weapon/scene but later exonerated with DNA. Lie detectors are just body rhythm detection, if you know how to set one off, you know how to not set one off and can get away with anything on them.
Not moving the body is good, if you're in a spot where evidence would be hard to find nice but what if not? You'll need a good place to dump a stiff, and the best spots are the least traveled such as at sea, middle of nowhere(desert terrain), or a place where no man walks ever deep in like the Montana back woods where you're more likely to find sasquatch than a corpse. The problem with moving is that you can leave evidence. I imagine one would need to be wearing gloves to leave their DNA off of the stiff, and second kill clean anything leaks/falls off is a problem so do that and have a big ass body bag or other garbage type bag to seal up things so you don't leave a trace. Another course that might work I suppose if not dumping it elsewhere, dump it local, find a nice tub of acid (kind of like The Dip drum in Roger Rabbit) and dissolve everything leaving no trace at all. In the end it's all about doing it clean and having a clean way to leave or disintegrate the body so no annoying bits of evidence are left behind.
