Detect bad shutdowns in OSX

Question

Is there a way to detect bad shutdowns in OS X?

The best I can come up with is parsing /var/log/system.log for lines like this:

12118 Jan 28 21:51:38 localhost bootlog[0]: BOOT_TIME 1422492698 0

without a previous line like this:

12112 Jan 28 20:39:58 Pauls-iMac.local shutdown[346]: SHUTDOWN_TIME: 1422488398 77104

What I have looked into

I share my computer with other users and I suspect some are not shutting down the computer correctly (i.e. turning it off at the wall instead of shutting it down correctly). So I want to detect the bad shutdown on the next boot.

I heard that OS X Server logs "Improper shutdown detected" in /var/logs/system.log, I think however, OS X does not. Surely there is some flag that is not set by the system following a bad shutdown (e.g. so that disk repairs can be performed by the system later).

I checked out dmesg which didn't have much (no timestamps either) and the logs in Console.app, but found no message that definitively indicated an improper shutdown.