Something else to consider is the size of the 12 yearl old
5'1 and 134 lbs??
That's one stocky 12 year old girl.
Perhaps the deputy reasoned that the potential for increased physical harm to her from the force needed to restrain such a large 12 year old justified the used of spray.?
Anyway, most police are trained on the use of escalation of force.
Let's take a look at the force scale.
Link
As taught by most law enforcement academies, the use-of-force continuum consists of five levels, with each tier representing an escalation in force from the preceding level. The principles of the continuum and safety considerations, as well as officer and department liability factors, reinforce the importance of approaching each situation on the lowest level possible to achieve the desired results. The escalation-in-force continuum model generally recognized in departments across the Nation is as follows:
1) Physical presence
2) Verbalization
3) Physical contact
4) Hand-held impact weapons
5) Lethal force.
While this model adequately reflects the methods available to police departments in past years, it does not accommodate the expanded arsenal of neutralizing agents available to today's law enforcement officers. Therefore, administrators and trainers should consider modifying the continuum to encompass these measures.
The new use-of-force continuum should include two additional levels and appear as such:
1) Physical presence
2) Verbalization
3) Less than physical force (neutralizing agents)
4) Physical contact
5) Less than physical force (neutralizing agents)
6) Hand-held impact weapons
7) Lethal force.
As reflected in this new model, neutralizing agents, such as pepper spray, can give officers an added degree of flexibility at two critical points in the force continuum--before they make any physical contact with subjects or after initial physical contact but before the introduction of hand-held weapons.
The deputy had tried 1 and 2 on the scale and they failed. Next up is either the 'less than physical force' or physical force.
I personally would rather have seen this 12 year old pepper sprayed than wearing a cast because the cop broke her arm or leg in a struggle.