On Fri, 27 Jan 2012 21:50:08 +0000, Steve Walker
wrote:

You lament to your teenage son that some ******* nicked all your tools
from your shed and drove off with them in a van. Your son tells a few
of his mates. The group of teenagers come across a parked van
containing tools that your son mistakes for the ones stolen from you.
He and his mates decide to grab them back. While they are doing so,
the bloke your son assumes is the thief starts shouting at them from a
rooftop. He and his mates shout back abuse at the supposed thief.

Is taking back the supposedly stolen tools acceptable vigilante
behaviour or not?

No. My (true) story was quite clear. He himself saw the tools being
stolen and who took them. Not second hand identification - the "rumour"
I mentioned. In your scenario, it is obvious that the son cannot know
for sure. As the tools are actually there, there is no problem with
calling the police and waiting - noting the van's reg. in case he drives
off.

You miss the point. In my scenario, your relative would have seen
*exactly* the same thing, and so been just as certain that his tools
were being taken by a thief, when in fact the person taking them fully
believed that he was perfectly entitled to take the tools.

The point is that even when it *appears* to be absolutely certain that
a crime is being committed, occassionally the witness is mistaken and
what they see is not what it appears to be.

--
Cynic