It is 100% legal, unless--and only if--prior to employees turning in the written complaints, the company had executed or signed some document or agreement agreeing to keep them confidential. Otherwise, in the absence of a confidentiality agreement of some kind, it is perfectly legal to give the complaints to anyone, even the accused.It is also not unethical: the company lawyer works for the *company*, not the complaining employees, and his/her duty is to the company. If the lawyer feels that turning the complaints over to the accused for the accused to review and respond to them is the best way to proceed for the company's benefit, that is not unethical.