From "Fundamentals of Criminal Investigation"

Terms such as "sodomy," "bestiality," "unnatural act," or "crime against nature" should be avoided.  In the preliminary phases words such as "contact," "caress," and "connection" will serve to create an atmosphere conducive to frank discussion.  After admissions have been obtained the interrogator can shift gradually to a restatement of the nature of the occurrence in terms of explicit, anatomical detail [...] The pathic or passive party in a sodomy case is usually the more vulnerable of the suspects.  In many cases, particularly if he is not confirmed in the sex habit, he will be under the impression that he is relatively innocent by comparison with his partner.  As in dealing with the active party, the investigator should not impart by his reactions any sense of the gravity of the offense.  Expressions of shock or abhorrence in the initial stage of the interrogation may strengthen the suspect's resolve to remain silent [...]