Susan, whot reported the effects of relativity on radioactive decay rate, and where was it published (details please)
The obvious effect is trivial. Take your radioactive sample, and your Gieger counter (or whatever you measure with. It depends on what the decay products are, as to how you detect them) and your clock for measuring the time and run with all of it at about 99% of the speed of light. Now just what time do you use in that t/tau? You can only see one clock, and what other clock agrees with it?.