If you are the target of an investigation - i.e. a suspect - you might be asked to take a polygraph. Should you take one or not? As you might guess - since this is advice from a lawyer - the answer is it depends.
The answer usually depends on why they are asking you to do it. They might be convinced you are guilty, and want you to take one and fail so they can get a confession out of you. Or they might hope to get a confession before you even take it. How do they do that? If you fail, they tell you the results, and use all the interrogation technigues they have been taught - which is usually to convince you that you'll be better off - and feel better - if you just admit what you did. Some police polygraphers also talk with the person before they even take the test, and convince them they would better off confessing before they take the polygraph and flunk it.
Sometimes investigators do not know who to believe. While this situation is rare, they might want something to fall back on - which would be a polygraph. This may happen in cases where it's not clear what happened, and there are two or more people telling equally convincing stories.
The problem with making this decision is that polygraphs are not always accurate - that's why they can't be used in court. A recent story shows that one particular machine has a history of problems that have largely been ignored. That means that you might fail even if you are telling the truth. If you truly are innocent and you fail, you suddenly become a suspect.
So do you look guilty if you refuse? Maybe - but what difference does it make. The police still have to investigate and obtain evidence. If you refuse they will probably look harder. On the other hand, you also appear guilty if you fail a polygraph - and most police officers won't even entertain the idea that the test was wrong.
The decision to take a polygraph is not one you should take without talking to a lawyer. Generally, if I don't know anything about the investigation my advice is always going to be not to take one. If I'm convinced the police simply want to use the polygraph to eliminate the individual as a potential suspect I might be more inclined to recommend it; that's only if I don't think there's a possibility the investigation will re-focus on them if they fail. The decision is not one that should be made without knowing as much as you can about the evidence - both from the police and the client.
Even if you do decide to take the polygraph, who administers it is important. It is best to have it done by someone not affiliated with law enforcement. It is even better to make arrangement for the test yourself.
You probably have more questions now than when you started reading this. There's a reason for that - as I said at the beginning the answer is it depends. You can only make the decision after knowing all the facts and evaluating the risks and rewards. An experienced lawyer is the best person to make that decision - it will be worth whatever you pay.