Well if you think about it, right, you've beat up some neighbour with a spade wearing masks and what not. Then in the short time span it takes someone to call the police and for the police to arrive you have to hide the evidence. Then there's the witness testimony's. Everyone's but yours is going to fit together, since at some point you had to go and get the mask and shovel. When the police find out that you have a alibi that doesn't match all the other's they're going to question you. Then they could get a warrant to search your house. There's going to be shoe marks near the body, there's going to be blood spatter transferred between the body and your clothes which, when you take the clothes off, will transfer to a part of your house. Then there maybe fibres that were already on your clothes, drop of, and land on the victim. Then when you go to burn the clothes, you have to buy fuel. And by that point the Police sorta know it's you. And fire doesn't consume all of the things you want to burn. They can still run various analytical techniques to determine the composition of what is left and then make a list of what might have these things in, which narrow's down the research. And then there the accelerant (cant spell it >_<) that you use to start the fire, which the gas/petrol station will have records of transaction and CCTV. Then it's just a matter of linking all the evidence back to you and any transfer evidence, and then linking that evidence to the victim.
Oh and you can't completely burn a spade. So they'll be able to match blood/tool marks to the victim, and possibly you.
Oh and you can't completely burn a spade. So they'll be able to match blood/tool marks to the victim, and possibly you.