We investigate the impact of conflicts of interests on randomised controlled trials in a game-theoretic framework. A researcher seeks to persuade an evaluator that the causal effect of a treatment outweighs its cost, to justify acceptance. The researcher can use private information to manipulate the experiment in three alternative ways: (i) sampling subjects based on their treatment effect, (ii) assigning subjects to treatment based on their baseline outcome, or (iii) selectively reporting experimental outcomes. The resulting biases have different welfare implications: for sufficiently high acceptance cost, in our binary illustration the evaluator loses in cases (i) and (iii) but benefits in case (ii).