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The international wildlife trade has caused significant declines in wild populations. Captive breeding can reduce the pressure on wild populations caused by overcollection, but if not properly monitored, wildlife laundering can lead to further population declines. Improving the forensic ability to detect wildlife laundering will assist in monitoring the wildlife trade and enforcing regulations, thereby aiding recovery of wild populations. Stable isotope analysis has grown in importance as a forensic tool, but improvements are needed. Here, stable isotope analysis (δ13C) on eggshells of captive bred and wild sourced island apple snails (Pomacea maculata) distinguished between the two; eggshells of captive bred snails were depleted in 13C relative to eggshells sourced from two wild populations. Thus, routine isotope sampling of eggshell material from purported captive breeding facilities can be used to identify discrepancies that would warrant further scrutiny. To address limitations of single-tissue stable isotope analysis as a forensic tool, I investigated between-tissue comparisons to differentiate between captive bred and wild sourced animals. The δ13C values of snail shell and foot muscle were significantly correlated in captive bred snails but not in wild caught snails. Between-tissue relationships therefore can detect wildlife laundering when animals are sampled in bulk. I also tested whether the use of hydroponically grown plants to reduce isotope variability in animal diets - and thereby in the tissues of the captive animals fed them - can increase the sensitivity of stable isotope analysis as a forensic tool. Kale grown hydroponically was significantly less variable in δ13C values than kale grown traditionally in soil. As predicted, P. maculata fed hydroponically grown kale had significantly less variable shell and foot δ13C values, and less variable δ15N foot values than snails fed traditionally grown kale. Combined, these experiments strengthen the viability of stable isotope analysis as a forensic tool capable of detecting signs of wildlife laundering.