Weasels are hard to catch. Especially in summer, bait goes off very quickly. Using life bait is not acceptable, unless it is a volunteer. This behaviour can possibly be encouraged by using a sealed bait bag with Brody pellets in it. As long as it is not damaged, the pellets with keep well and are attractive to mice (and rats). Mice won’t set off a DOC200, but if they nibble on the pellets and a weasel come passed it may (try to) catch the mouse. If the trap is a ‘soft touch’ the weasel will get caught and the mouse may come back for the bait. If the weasel doesn’t get caught on the way in, it may do so while carrying the mouse after catching it. I only found out because I put a bag of Brody in a DOC200 because I had no other bait and there was no other bait in the trap. When I came back a week later, it had caught a weasel. After close inspection of the bait bag, I found some minuscule puncture holes in it, most likely from the living bait (mouse). There are probably lots of rules around this in DOC of Council controlled areas, but it may be an option in private area.
We have caught two weasels recently on our beta long life lures using Vic Proff traps. We are interested in providing lures if anyone wishes to trial them for weasels. The baits last about three months. admin@rattek.com
As Willem states above the belief is that when you attract mice you may also get weasels so we recommend a long life lure ( preferably ours 
and a guard like the one sold by TrapTools. This stops mice taking your bait but with some luck they will come back and forth giving it a go. This all requires that you have a trap that wont be set of by the mice transit.
I’ve caught them in victors a number of times with cooked/raw pork fat, works pretty well and attracts rats and mice too if your also targeting them. Had clean kills too.
We have caught +150 weasels in one of our local projects, far more weasels than any other mustelid. They have mostly been in double-set DOC200s, but still around 20 in unbaited DOC150 run-through style tunnels.
In the baited tunnels they have been caught on a variety of commonly used bait types: egg 12%; Erayz 22%; fresh beef or venison meat 15%; peanut butter 12%; but the highest number have been caught on rabbit/hare meat at 38%. So the combined meat bait types (mostly fresh but some salted) accounted for more than half the weasel captures.
I find that weasels are likely to be caught in areas of long rank grass, where presumably there are mice, skinks, & invertebrates for them to eat.
So targeting them with fresh meat in or on the edge of areas of long grass seems to catch well. And having well calibrated traps that mechanically function smoothly.