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interview; but if you are convinced, or become so by 
talking with them, that they have knowledge of important 
facts which they have an interest in keeping from you, it 
is often wiser to postpone the serious attempt to get these 
facts until it is possible to do so under more favorable 
circumstances. On the other hand, it is desirable to 
question such witnesses, when possible, before they learn 
that they are suspected and have time to talk to each other. 
At least try to prevent communication between the 
witnesses until you have questioned them separately. 
Special care must be exercised to interview a group of 
related witnesses in the best order to prevent collusion 
between them. It is usually best not to interview two or 
more hostile witnesses together. Keep them apart and 
interview them separately whenever possible. 
Always conduct interviews with an enemy to your case 
strictly as an official. Be courteous, but do not introduce 
everybody all round, or joke, or in any other way help to 
put the witness at his ease. Especially when the time has 
come to hammer hard for the facts or for a confession it 
greatly helps to surround the occasion with as much cir¬ 
cumstance and formality as you can bring to bear. Have 
your own witnesses and assistants at hand; the more of 
them who are unknown to the person to be interrogated, or 
known only as officials, the better. A witness who is 
either the suspect or his accomplice or sympathizer, as is 
here assumed, will deceive you if he can and will not tell 
you the truth unless you can entangle him or otherwise 
bring pressure enough upon him to compel him to do so. 
One of the most valuable helps in this is to increase his 
nervous tension by every legitimate means. 
Keep your notebook out and take time to record every¬ 
thing necessary or significant. Write down a minute 
description of suspects. This may be valuable to you and 
should form a part of the case record in any event. If you 
ask the witness, in connection with this record, for his age 
and make other pertinent points, it will usually help to 
increase his sense of the gravity of the case. Mental states 
go in waves, however, and it is possible to overstay the 
crest. The effect of everything upon the witness should 
