Huge Gym, Spot inbound play

[johnyd]

Highschool JV girls, spot inbound play on end line. Biggest H.S. gym I was ever in. Defender very close to the line but not violating. Inbounder backs off end line 5 steps. I have to back up as to not interrupt throw in. I deliver the ball and start the count.

The girls takes 3 giant strides straight forward toward the end line and throws the ball 2 hand over head while sliding the back leg just like a soccer inbound throw. Is 3 steps directly forward, toward end line a violation?

I made no call. Help please. What's the rule?