minor sexual abuse

My daughter who is 11 and a half has accused my cousins son who is 15 of sexually abusing her during a family get together. The problem is that I don't know if I believe her. My cousins son is denying the accusation. I am told by the County Sheriff's Dept. that he most likely will be booked for this crime, and that they may request a lie detector test. Can I, or do I have the right to, request that my daughter also submit to this testing as well???
I live in Washington.
HELP

You seem to be a very supportive parent.

There is no such thing as minor sexual abuse -
As a mother I would believe MY CHILD before I believed the so called abuser. I pray your daughter can forgive your lack of trust/support. Don't be surprised if she never comes to you again.