Drawn from several articles:

Lanza went after the first grade classes because those were the children his mother spent so much time with as a volunteer last year.

I read that he shot his mother four times. Over 100 shots were fired. 26 were killed at the school. Four shots per body.

The bodies could not be moved because everything had to be carefully catalogued before anything could be removed.

Over 50 shell cartridges per classroom.

Let's say 20 dead and wounded per classroom. Multiply that by at least a quart of blood each. Now try this at home: Go into a room you don't use and pour 20 quarts of water on the floor, then jump around in it and splatter it everywhere.

20 dead and wounded with .223 caliber bullets at very close range would create a horrific amount of bone and tissue fragments everywhere. That would all have to be catalogued.

The police would have to try to recreate the crime scene. That means going in and trying to rearrange all of the furniture (even if only mentally) then imagine where everyone was, then try to figure out what everyone did when the shooting began, they try to figure out step by step who was shot when.

All of the ballistics in the rooms have to be measured. That means recovering spent bullets, bullet fragments, and trying to match bodies with bullets and trajectories with bullets.

That is why the bodies were left for over two days.

Now, even though Lanza is dead, that all has to be done by law because it is a crime scene. And especially if there is someone else who could be charged, someone who may have acted as an accomplice, that evidence is all vital.

No energy harvesting; nothing nefarious.