Are you the sort who likes a bit of academia with your Death Note?
One who can make allowances for fictional elements in a fictional world, but otherwise demands that the realism stands up to scrutiny, consistent within the mores of its own universe?
I wouldn't be at all surprised if you were. There are a lot of us around.
All to be expected when our common denominator is readership of a story wherein intelligence is glorified.
Death Note is all about cleverness, pitting wits against wits, problem solving and staving off boredom with innovative new ways of looking at the world.
Most of the major characters aren't merely smart, they are professed geniuses. Light Yagami is Japan's highest scoring student. L, Near, Mello and Matt - his antagonists - were all raised in Wammy's House for Gifted and Talented Orphans. Whichever team you cheer along, the act you're cheering on is bound to be rooted in high performance brain power.
It's the nature of the game.
I've written 11th fan-fiction novels based upon the plot-holes, inconsistencies and scuffed over leaps of narrative, which I uncovered approaching from Death Note from a humanities perspective. Great central construct; pity about the execution.
It seems that the hard science of Death Note equally fails under scrutiny too, as Applied Computer Scientist, researcher, programmer, scholar and statistician Gwern has discovered. (S)he has laid it all out in the recently updated essay Death Note: L, Anonymity and Eluding Entropy.
Complete with proper citations, appendices and transparent mathematics (where appropriate), Gwern not only highlights all of the occasions when Light, L et al got it woefully wrong, but follows through with how they might have approached the same problems with a modicum of success. Or, at least, some kind of regard towards real world laws of probability, differentials and other such terms that mere historians like me only barely grasp as a concept.
Moreover, Gwern points out all the noob errors that should have had Light arrested within about the first two chapters. Better still, the essay includes invaluable tips on anonymizing oneself online and maintaining personal privacy.
Forget Death Note! This is priceless information to take on board ourselves, applicable as good practice regardless of whether we're attempting to cover up mass murder with a notebook.
I thoroughly recommend going to check it out. Thanks, Gwern!