Public Law & Legal Theory
Legal rules severely restrict payments to fact witnesses, though the government can often offer plea bargains or other nonmonetary inducements to encourage testimony. This asymmetry is something of a puzzle, for most asymmetries in criminal law favor the defendant. The asymmetry seems to disappear where physical evidence is at issue, though most such evidence can be compelled and need not be purchased. Another asymmetry concerns advance payment for likely witnesses, as opposed to monetary inducements once the content of the required testimony is known. One goal of this Article is to understand the various asymmetries—monetary/nonmonetary, prosecution/defense, ex ante/ex post, and testimonial/physical—and another is to suggest ways in which law could better encourage the production of evidence, and thus the efficient reduction of crime, with a relaxation of the rule barring payment.
Saul Levmore & Ariel Porat, "Asymmetries and Incentives in Evidence Production," University of Chicago Public Law & Legal Theory Working Paper, No. 379 (2012).