I don't follow the first example about jury deliberation. Isn't the criticism in that case about the method which might harm the behavior of the jury and not about the knowledge gained? I guess that the point is that it renders research impossible if there is no available method but this does not seem to support the argument that the topic of research is possibly immoral.

The author isn't claiming that the topic of research is immoral. W.r.t. the jury example, she writes that "the topic is interesting, morally unobjectionable methods are available and some practical profits are reasonably expected." She is arguing that methods such a those that involve recordings are not themselves the cause of harm because problems only begin when there is a knowing agent at the terminus of the method of observation used. No violation of secrecy occurs if the recordings are never watched. Yes, the method is incomprehensible without the end, but we can still distinguish the means from the end and it is the end that violates the condition of secrecy, not this method of data collection itself.

Of course, concealing the presence of recording devices may prevent the jury from finding out about the violation of secrecy, but the violation happens nonetheless as a matter of objective fact and this could itself constitute a breach of ethics. Furthermore, news of the violation could or even would eventually get out (esp. if results are published) and affect future jurors. However, in her example, the author assumes that consent has been secured which naturally entails that the jurors know about the violation of secrecy.