The Civil Rights Office of the United States Department of Transportation ("DOT") has a written policy that helps its employees understand how one can tell if conduct is "unwelcome."  I like the DOT’s policy because it gives employees some practical advice on how to convey that inappropriate sexual comments or conduct is unwanted.  

The policy states that "Only unwelcome conduct can be sexual harassment.  Consensual dating, joking, and touching, for example, are not harassment if they are welcomed by the persons involved." 

"Conduct is unwelcome if the recipient did not initiate it and regards it as offensive.  Some sexual advances (“come here Babe and give me some of that”) are so crude and blatant that the advance itself shows its unwelcomeness.  In a more typical case, however, the welcomeness of the conduct will depend on the recipient’s reaction to it."

Outright Rejection:  The clearest case is when an employee tells a potential harasser that conduct is unwelcome and makes the employee uncomfortable.  It is very difficult for a harasser to explain away offensive conduct by saying, “She said no, but I know that she really meant yes.”  A second-best approach is for the offended employee to consistently refuse to participate in the unwelcome conduct.  A woman who shakes her head “no” and walks away when asked for a date has made her response clear.

Ambiguous Rejection:  Matters are more complicated when an offended employee fails to communicate clearly.  All of us, for reasons of politeness, fear, or indecision, sometimes fail to make our true feelings known.  A woman asked out for a “romantic” dinner by her boss may say, “Not tonight, I have a previous commitment” when what she really means is “no way, not ever.”  The invitation is not inherently offensive, and the response leaves open to question whether the conduct was truly unwelcome.

Soured Romance:  Sexual relationships among employees often raise difficult issues as to whether continuing sexual advances are welcome.  Employees have the right to end such relationships at any time without fear of retaliation on the job, so that conduct that once was welcome is now unwelcome.  However, because of the previous relationship, it is important that the unwelcomeness of further sexual advances be made very clear.

Sexual harassment investigations sometimes fall within a gray area where the comments were "boorish" or "childish."  It may not be readily apparent if the conduct was consensual, or if the Complainant was truly offended but the Complainant neither did or said anything to convey to the accused that he/she was offended and that the harasser should stop.  A sexual harassment investigator will need to probe into the past relationship of the parties to determine if they have had past interactions which might have led the accused harasser to believe that his/her conduct was welcomed.  Soured romantic relationships, especially if they are on-again, off-again pose a particular set of problems that require close scrutiny by the sexual harassment investigator.