This paper is about the incentive effects of legal presumptions. We analyze three interrelated effects of legal presumptions in a tort setting: (1) incentives to invest in evidence technology; (2) incentives to invest in care-type precautions; and (3) incentives to mitigate excessive activity levels. We suggest that the overlooked interaction between evidence and substantive tort rules is an important dimension that should inform the choice of legal presumptions. After considering the traditional factors that guide the choice of legal presumptions in tort law, we introduce the concept of “best discovery-bearer” to capture some of the factors that should guide the choice of legal presumptions. According to our analysis, the best-discovery-bearer criterion requires a shift of the burden of proof to the parties (a) who can most effectively invest in evidence technology; (b) whose precautions are more inelastic relative to discovery errors; and (c) who are not already burdened by the residual liability.