Victim is now 17 years old but at 16, her and a 21 year old had sex.
Can he be charged for Statutory rape even if she didnt refuse at the
time and would there need to be evidence to support her?

Dear Outcast, 

The concept of "statutory rape" discusses a situation, where one has
sex with a person who  has not reached the statutory age of consent,
even if the minor has participated in the intercourse willingly. In
other words, one could be charged with statutory rape, even if there
has been concent.

In Missouri, if a person who's 21 and over has sexual intercourse with
someone younger than 17, they could be charged with statutory rape
second degree (a Class C felony), regardless of consent. If the person
in your case was less than 21 of age at the time of the alleged
intercourse, they cannot be charged.

As for proof or evidence, any defendant has the right to deny the
charges and request the prosecution to present evidence against
him/her. If the person over 21, for example, denies that they have
ever had sexual intercourse with the minor, the burden of proof is on
the prosecution: they have to produce evidence, either by letting the
victim testify, or otherwise.

See: 
Section 566-034 - Statutory Rape, Second Degree
<http://www.moga.state.mo.us/statutes/C500-599/5660000034.HTM> 

University of Missouri - Missouri Sex Offences
<http://web.missouri.edu/~stulife/stu-org/cawww/sls/lc/wwwTips/SexOffenses.html> 

I hope this answers your question. Please contact me if you need any
clarification on this answer before you rate it. My search terms:
"class c felony" "statutory rape" Missouri, "class c felony"
"statutory rape Missouri, "class c felony" in Missouri,

http://www.smith-lawfirm.com/sol_Missouri.html

The Missouri statute of limitations for child sexual abuse is 3 years
or before the age of 30.  You are within the statute of limitations
and the definition of statutory rape, however, the question here, as
the previous poster has stated, is whether you will be able to present
enough evidence to convict the defendant.

Personally, I would focus your effort on rehabilitating the child and
teaching the child to conduct themselves in a way that would not leave
them susceptible to these types of situations.  The child was
consenting regardless of what he/she feels now and regardless of what
the law says.  In reality, this day in age, a 16 year old should have
some common sense and take responsibility for their own actions.  Both
people involved were partially to blame, by attempting to spitefully
hurt someone else's reputation for something your child was
[debatably] equally to blame for will possibly teach them that it is
ok to blame other people for bad life decisions that he/she makes and
this could wind up causing even more psychological problems for the
child than this initial experience may have.  But that's just my
opinion so do whatever your heart desires because our wonderfully
flawed personalities and legal system has made it possible for you to
take advantage of.

What victim.  There is not victim in statutory.  It is consentual.

Nelson-ga,
Sorry, you are wrong.  That is what the (above) subject is about: 
that the statute defines sexual intercourse as rape if the person (we
assume, the girl) is younger than a certain age, or until a certain
age if the difference in ages is a certain number of years  -
regardless of consent.  And furthermore, "rape" can be defined then in
"more generous" terms such as "carnal knowledge", which includes heavy
petting by most folks' understanding of the expression.

Fact is, the laws in many states and countries have been changed  - or
re-interpreted by the courts -  to give greater respect to youthful
consent.  Back when I had to worry about it, I believe(d ;) ) in Mass.
that statutory rape was sex or carnal knowledge with a girl before she
was 18.  There was some opinion that if a defendant could prove that
she had "been with" four other males, that was an adequate defense.
Myoarin

I was speaking not from a legal perspective, but from a common sense one.

I'm not a lawyer, but I believe the idea behind statutory rape is the
minor doesn't really know what sex is- esp. the long term
consequences- and therefore can't consent to it.