Contamination is the root cause of false confessions. Confessions/admissions should be independently verifiable by eliciting information from the offender that only the offender would know. Questions contaminate responses. The questioner's response to answers contaminates responses. So, questions have to be carefully constructed and all possible sources of contamination need to be minimized. Careful selection of the interview room; the number of people in the interview; making sure only one person conducts all interviews; careful construction of questions; using only mutually understood words in the questions are a few examples.