Some isotopes have stable half-lives. They use this to estimate the age of the organic material the isotopes used to belong to. What about it is a sham?
Like all tenets of evolutionary theory, radiometric dating is founded on wishful thinking and unverifiable assumptions:
assumption #1: radioactive decay is constant over millions of years
assumption #2: the quantities of radioactive material and daughter substances are constant in a given soil sample, not subject to affects of leaching in or out.
assumption #3: The components of a given lava flow consist of 100% of the radioactive substance and 0% of the daughter substance.
In truth, the only way to verify the accuracy of radiometric testing is to measure blindly a substance of known age and compare the results. Example: An Egyptian mummy known to be 5,000 years old could be tested using C14 dating. It's important to realize that even if the test were dead accurate at 5,000 years, that in no way verifies the the test is accurate for a sample 10,000 years old. Those types of extrapolations constitute bogus science.
In the case of radiometric dating, mutliple blind trials have been conducted on known lava flows ranging in age from ~25 years (Mt. St. Helens), to Kilauea (circa 200 years, to ancient volcanoes of known dates. All of these have revealed extremely spurious results, with estimated ages of 100,000 years to over 2 million years.
The evos counter this with the argument that these dates are only estimates and are not reliable for dates of less than 2 million years. The fact is, the labs report these values. If these values were not thought to be accurate, they would not report them. Instead, the result would read "0 to 2,000,000 years", not "500,000 to 2,000,000 years".
The hypocrisy of evolutionary thinking is further revealed by their insistence that "pre-human" ancestors such as Australopithecus are accurately dated at 2 million years, when in the same breath they brush off arguments against radiometric dating with the excuse that is is not accurate for dates of less than 2 million years.