An Investigation into Compound Likelihood Ratios for Forensic DNA Mixtures.

Simple propositions are defined as those with one POI and the remaining contributors unknown under Hp and all unknown contributors under Ha. Conditional propositions are defined as those with one POI, one or more assumed contributors, and the remaining contributors (if any) unknown under Hp, and the assumed contributor(s) and N unknown contributors under Ha. In this study, compound propositions are those with multiple POI and the remaining contributors unknown under Hp and all unknown contributors under Ha. We study the performance of these three proposition sets on thirty-two samples (two laboratories × four NOCs × four mixtures) consisting of four mixtures, each with N = 2, N = 3, N = 4, and N = 5 contributors using the probabilistic genotyping software, STRmix™. In this study, it was found that conditional propositions have a much higher ability to differentiate true from false donors than simple propositions. Compound propositions can misstate the weight of evidence given the propositions strongly in either direction.

Do You Get What You Paid For? An Examination of Products Advertised as Kratom.

Although some novel psychoactive substances (NPS) are newly discovered chemicals, others are traditional or indigenous substances that are introduced to new markets. One of these latter substances is a plant many people refer to as kratom. Indigenous to Southeast Asia and used for a variety of instrumental and recreational purposes, kratom has recently become available to Western drug users. Kratom is somewhat unique in that the plant contains two different psychoactive chemicals, which have both stimulant (mitragynine) and narcotic (7-hydroxymitragynine) properties. Thus, kratom may appeal to different types of drug users for reasons other than curiosity. In the current study, 15 samples of products that were either directly advertised as kratom or were listed in the results of a web search (but were not directly advertised as kratom) were purchased for testing. After laboratory testing, it was determined that all products advertised as kratom contained the active chemical mitragynine, but 7-hydroxymitragynine was not detected in any of the samples. Implications are discussed.