Forensic Metrology A short introduction

1. Forensic MetrologyA short introduction Veronica Scotti

2. Forensic science Forensic science is the application of scientific principles and technological practices to the purpose of justice in the study and resolution of criminal, civil and regulatory issues Bylaws, American Academy of Forensic Sciences When scientific testimony is offered, the proponent must prove the testimony is produced by valid, scientific techniques and that the process or system produced an accurate result Imwinkelried, Exculpatory Evidence, sect. 6-4, Michie Co., 1990 Both definitions outline that up-to-date scientific principles and technological practices must be referred to, to produce an accurate result

3. Forensic metrology • Test and measurements have become more and more used tools in forensic sciences • Metrology is the science of measurements • The basic principles of metrology and its best practice cannot be neglected when scientific testimony is offered, based on the result of tests and measurements • Forensic metrology is that branch of forensic sciences that deals with the correct way of performing measurements and presenting their results • This video tutorial will explain the main principles of forensic metrology and why it helps justice to ascertain the factual truth

4. The pillars of metrology • Metrology lies on three main pillars: • Uncertainty • Calibration • Traceability • Measurement results will never provide the true value of the measurand • When measurements are performed considering these three pillars in a correct way, the measurement result is given as an interval of possible values into which the value that could reasonably be attributed to the measurand is expected to lie with a given probability. • It can be obtained from uncertainty • This probability is related to the probability that the measurand value lies outside the provided interval • Probability of wrong decision

5. How metrology helps justice • Measurement results provided absent uncertainty keep an important element hidden to the trier of facts: the probability of wrong decision • Decisions cannot be taken beyond any reasonable doubt, because the existence of doubts is not revealed to the trier of facts • Measurement results provided together with uncertainty quantify the doubt about the correctness of the results • The trier of facts can now decide, according to his or her conscience, whether the doubt is reasonable or not • Complete information is provided

6. Examples • A couple of examples are given where uncertainty was not evaluated or provided, and wrong decisions could have been taken. • The Liverpool bartender case • The Perugia murder