In a murder trial in the $1990$s$,$ the defendant$$s blood was found at the crime scene. The prosecutor argued that blood was left by the defendant during the crime. Defense argued that police $$planted$$ the defendant$$s blood from a sample collected later. Blood is normally collected in a vial containing the metal$-$binding compound EDTA $($as an anticoagulant$)$ at a concentration of ~$4\mathrm{.}5$ mM~$4\mathrm{.}5$ for a vial filled with blood. In the $1990$s$,$ procedures to measure EDTA in blood were

not well established. Even though the amount of EDTA found in the crime$-$scene blood was orders of magnitude below

$4\mathrm{.}5$ mM$,4\mathrm{.}5$ mM$,$ the jury acquitted the defendant. This trial motivated the development of a new method to measure EDTA

in blood.

a$.$ Precision and accuracy. To measure the precision and accuracy of the method, blood was fortified with EDTA to

known levels.