For example, C14 leaches at an accelerated rate from organic material saturated in water, especially saline water.
Fourthly, for C14 to test accurately the artefact must have been protected from contamination.
Organic matter, being porous, can easily be contaminated by organic carbon in groundwater.
This increases the C12 content and interferes with the carbon ratio.
Some examples of abnormal C14 results include testing of recently harvested, live mollusc shells from the Hawaiian coast that showed that they had died 2000 years ago and snail shells just killed in Nevada, USA, dated in at 27,000 years old.