Anyone can at some point, without doing anything wrong, have some problem with the Spanish legal system. Also in Spain you are always innocent until the contrary is proven. The Spanish Constitution guarantees equal right for legal assistance and protection for any person.
This can be either as a victim, in which case it is very important to know your rights and to be able to claim whatever you are entitled to. Therefore it is important to have professional assistance in your own language.
Also you can be accused of a criminal or misdemeanor offence. Keep in mind that for instance if you by accident knock down someone with your car this can be considered a criminal offence punished by prison!!! Also in these cases you are entitled to defend yourself, and it is important to get the best help possible, and in your own language.