Marketing firms navigate a dynamic environment characterized with volatility and complexity, where survival hinges upon adaptability and responsiveness to external forces. The pursuit of rapid growth, profit and competitive advantage in the cosmetics market often leads some companies to engage in unlawful and unethical practices, including copyright and trademark infringement and misleading marketing, which creates problems for honest consumers and the entire industry’s sustainability and leads to legal cases of fraud. This has led to the emergence of a specific type of marketing ‒ forensic marketing, characterised by a thorough check (often in a legal context) of all the facts and data accompanying marketing policy. This study examines how forensic marketing dimension influence the consumer behavior using the case study of 3 skincare products in Nigeria, including the impact of copyright violation on brand awareness, trademark infringement on consumer patronage, and the impact of misleading advertising on consumer loyalty. In solving this problem, the article analyses the provisions of the Theory of Buyer Behaviour, the Nicosia Model and the Psychoanalytic Model. The study is based on the results of an online survey of 384 Nigerian consumers of cosmetic skincare products (a five-point Likert scale was used for answers, Bill Golden technique was used to determine the sample size, Cronbach’s Alpha test was used to confirm reliability, and SmartPLS software was used for data processing). Descriptive (frequency, percentage, mean, standard deviation, and skewness) and inferential (structural equation modelling (SEM) by utilising the partial least squares (PLS) version) analyses were carried out. The modelling empirically confirms the validity of all three hypotheses: 1) respondents perceive copyright infringement as having a significant relationship with brand awareness, with the strongest impact on a product idea, moderate impact on brand name, and weak impact on promotion strategy; 2) trademark infringement practices have a significant impact on consumer patronage, with design having the strongest impact, signs and symbols having a moderate impact, and colour having a weak impact; 3) deceptive marketing practices have a significant impact on customer loyalty, with advertising having the most significant impact, product quality having a moderate impact, and labelling and packaging having a weak impact. The article emphasises the importance of regularly informing consumers about the quality and features of products, as well as encouraging whistleblowers through reward systems. By adopting ethical marketing practices, companies can build a reputation that will ultimately benefit society, strengthen their reputation, and influence consumer purchasing decisions.