I WOULD agree to lowering the minimum age of criminal liability from 15 years old to 12 years old, but not 9 years old.
The reason why I would choose the age of 12 years for a child to be criminally liable is based on two factors: education and environment.
Under the Philippine K to 12 education standards children are required to undergo one (1) year kindergarten, six (6) years elementary, four (4) years Junior High school and two (2) years Senior High school. Also the age requirements imposed by the K12 program are as follows: age 05: Kindergarten, age 06: Grade 1, age 07: Grade 2, age 08: Grade 3, age 09: Grade 4, age 10: Grade 5, age 11: Grade 6, age 12: Grade 7 (First Year Junior High School), age 13: Grade 8 (Second Year Junior High School), age 14: Grade 9 (Third Year Junior High School), age 15: Grade 10 (Fourth Year Junior High School), age 16: Grade 11 (First Year Senior High School), age 17: Grade 12 (Second Year Senior High School).
From the above we can see plainly that at age 9 a child, if he/she is in school, would just be in grade 4 and would still be starting to learn things in his immediate environment. The possibility of outside interference (from the environment) which might sway and influence the actions and behavior of such a young child is still quite minimal. The likelihood of a 9 year old child engaging voluntarily and with discernment in certain serious criminal acts is quite small considering the very limited environment to which he/she is exposed.
Compare this with a child who is already 12 years old and, if in school, already in Grade 7 or First Year Junior High School. This child will already be exposed to a much wider environment with greater influences and temptations. It is usually at this stage where an elementary graduate is introduced to the complexities of the high school life. This is also usually the period where a 12 year old child starts to feel and be burdened with so called peer pressure and will sometimes give in to the temptation of rebelling against parental authority.
Of course, it might be entirely different if there are no parents to speak of and against whom to rebel against. In this case society can become a suitable substitute and this is where it gets dangerous because of the high possibility of third party involvement (e.g. public) that may lead to grave consequences. It is at this age when a child is suddenly thrust into an expansive environment and higher education (high school) and where he starts to realize the significance of having friends (barkada) and of the burden of peer pressure that would oftentimes dictate his behavior and actions.
And so because of this and of the desire not only to protect society but also to see to the welfare of children and minors the minimum age of criminal liability should be lowered but not 9 years old as approved by the House Committee on Justice but instead 12 years old.