Abstract: A method and a system for grading the confidence of a result of an experiment that comprises one or more biological and/or chemical reactions and is carried out in a microchannel structure (110a) of a microfluidic device, said confidence determination comprises the steps of: i) detecting within each of at least one liquid detector segment of said microchannel structure (110a) the presence or absence of liquid and/or gas during a period of time for which it is known if liquid and/or gas shall be present and/or absent in the segment, and ii) assigning a lowered confidence to said result if the presence and/or absence of liquid and/or gas found in step (i) is deviating from what it shall be.