Why does my pan always splatter when I make chicken breasts?
The reason why fried meat splatters is that correct frying temperatures (~ 180 Celsius pan surface) are well above the vaporizing temperature of water (100 Celsius). Each droplet of cell plasma which comes into contact with the frying fat creates a tiny steam explosion. And explosions splatter. 

If you were meaning to ask not why it splatters, but how to prevent it: you can't. See also the existing question about it. 

On a side note, 12-14 minutes per side of chicken breast sounds like you are reducing it to particleboard. See this question for correct internal temepratures.