How do I tell if an NPC is essential?

I received the "Lights out!" quest from Jaree-Ra, but it does not match with the personality of my characters. Since I cannot report him to any guard or other authority, I decided to kill him without doing the quest in order to see what happens. However, I assume that he is marked as essential.

How can i check if an NPC is marked as essential or not without dropping them to low HP before realizing they cannot be killed?
Console commands are an option.

I know there is a console command to set them to non-essential but I am specifically trying to check their essential status in advance.

According to this wiki of Skyrim console commands, you can select the NPC in question (generally using your cursor) and enter the command IsEssential which will return 1.00 if they are, in fact, essential.

Related functions: To check whether an NPC is essential to begin with, select him/her in the console (so that the ref ID appears), and enter IsEssential - if the console returns "1.00", the NPC is essential.

If you have 100 points in Pickpocketing and the perk that allows you to pickpocket equipped items, you can test them. You will not be able to remove equipped items on essential NPCs, even with the trait.

Source: http://www.uesp.net/wiki/Skyrim:Essential_NPCs

An alternative way to do this using the console is to use the kill command on them. You avoid combat, and if you want them dead and they aren't essential they will be dead. Otherwise they will lay on the ground for awhile. To use the kill command open the console and click on the target then type kill and hit enter.