Isn't Carbon Dating Unreliable?
Radiocarbon dating is just one of many "radiometric" dating techniques. While contamination in the laboratory might happen on rare occasions, radiometric dating remains a trusted and reliable method of determining the age of a sample. The technique relies on the constant rate of decay of certain radioactive elements in the sample. For example, rubidium-strontium dating relies on the decay of rubidium-87 to strontium-87. Rubidium-87 has a half-life of 50 million years (the amount of time for half its mass to decay into strontium). Using this figure, scientists measure the amount of rubidium and strontium in a sample to determine its age.
[ References: Wikipedia: Radiometric Dating ]