The study examines how an individual's level of fraud detection proficiency (an individual possessing formal fraud education or training, informal fraud training, fraud task-specific experience, and /or fraud-related certifications) impacts their performance on fraud risk assessments and modification of audit plans. Further, it explores which of the fraud detection proficiency dimensions are valuable for auditors in situations of high and low levels of fraud risk and how these characteristics interact with professional skepticism. This, as well as the effectiveness and efficiency of the procedures selected, are addressed using a survey-based scenario where one case is embedded with a financial statement fraud and the other is not. Tobit and ordered logit regression models are used to evaluate a sample of 40 auditors and 10 forensic professionals with varying levels of fraud-related experiences, education, training, and certifications against a benchmark panel. Results demonstrate fraud certifications are effective in fraud risk assessments, are not effective in audit plan modifications, and on average those individuals tend to over-audit. In addition, fraud-related task-specific experience improves audit plan modification effectiveness. Third, including professional skepticism as an interaction is more reflective of the variable's nature, with results supporting interactions with fraud certifications and informal fraud training in the fraud risk assessment model and formal fraud training in the audit plan modifications model. Finally, individuals of higher rank, in addition to those with fraud certifications, are more likely to over-audit, while individuals in the no fraud scenario are more likely to under-audit. This study contributes to the academic literature with regard to a subset of the FJDM proposed by Hammersley (2011) validating professional skepticism as an integral variable in the model, particularly as an interaction variable and with regard to the impacts of fraud certifications and fraud-related task-specific experience. The study also contributes by providing evidence, which indicate lower fraud risk situations are prone to assessing fraud risk less effectively and under-auditing. Finally, this study also contributes a new measure for direct fraud-related experience, which captures more details regarding applicable task-specific experiences. / Ph. D.