Originally Posted by djaffinito
I've never had kill -9 create a zombie personally, I use it on a daily basis.
Try kill -15 or just kill. It defaults to signal 15. Then up-arrow and re-issue that kill after a short moment. If it was well behaved and cleaned-up and exited, or simply exited, your next kill will get "No such process" as confirmation that it went away. If not, then you can grab the larger hammer and whack it with kill -9.
If you want to know what a process is doing you can trace its system calls with strace -p <PID>.
Of course kill and trace only work for the processes owned by your UID... unless you're root.