Forestry Commission snaring trials in 1968/9 comparing free running and self locking snares in Scotland found “little difference in suffering caused by each snare.” Post mortem damage, often significant was similar for both types of snare and of 153 foxes caught, 132 other animals were caught, amongst which were 3 rare wild cats, one feral cat, 30 mountain hares, 21 deer, and 50 brown hare, and 3 dogs. Only 4 badgers, but that was due to the Scottish location.
Despite both snares being proved to be cruel and indiscriminate, the 1981 Wildlife and Countryside Act only banned self locking snares.