tear sheets are normally from a paid to shoot expressly for publication purpose. To use one from an obituary would be seen as a bit of a desperate claim on one.
Now maybe if one was hired to take the shot after they died, but I still wouldn't use it.
You use a tear sheet to help get you jobs. If the jobs you are trying to get are taking photos of people so they have something good to use for their obituary photo, then it works. Not exactly conventional, but I guess everyone is a possible customer ;P
Sitting on the fence for a moment, I think it depends a little on the circumstances.
If the image in the publication was of a celeb and one of your portrait images was used for the obit and it was printed nice and large and was a feature on that celebs life.
Then in one way I will feel a bit honoured that out of all the 10s of thousands of images of that celeb mine had been used to celebrate their life at the end of it.
Its still a bit dark to use as a tear sheet...
but if its a little standard obit column, with a little photo of someone then that is really desperately scrapping the barrel for images....