In many instances, you can also be required to provide samples of hair, skin, blood and other bodily fluids, and handwriting, although you should not provide those things voluntarily, or consent to their being taken, without talking to a lawyer first. In such cases, you get to select the type of sample you want to provide. If you don't choose, the police will choose for you and will normally select a blood test. Never try to resist, or interfere with, a search no matter how unlawful you believe it to be . Being arrested, searched and jailed, can be very traumatic even in the best of circumstances.
Most people are badly shaken-up, and rattled, by the experience.
It is frightening, embarrassing, humiliating. If it happens to you, you may not be thinking clearly. The police understand that and, typically, try to capitalize on that fact and take advantage of your vulnerability. Remember, they may be lying to you. You may not have a true picture of what has happened, what's going on, or what they're up to.