Short answer. Possibly yes. Article 17 of the Revised Penal Code does not require that you were at the scene. You can be a principal by directly inducing another to commit the crime, or by cooperating through an act without which it could not have been accomplished. Planning alone is not automatically enough.
What the law says
The following are considered principals: 1. Those who take a direct part in the execution of the act; 2. Those who directly force or induce others to commit it; 3. Those who cooperate in the commission of the offense by another act without which it would not have been accomplished.
Revised Penal Code, Article 17 — Who Counts As Principal. Read the full provision →
Three ways to be a principal — only one needs you present
The article lists Those who take a direct part in the execution of the act, Those who directly force or induce others to commit it, and Those who cooperate in the commission of the offense by another act without which it would not have been accomplished. Only the first describes the person physically at the scene doing the deed. The second and third describe people who may have been miles away when it happened. So the sentence I was not there does not by itself answer a charge of being a principal. It closes off one of three routes and leaves two open.
Inducement has to be more than encouragement
The wording is that the person must directly force or induce another. That contemplates a command, a price, or pressure strong enough to move the other person to act, coming from someone whose word carries that kind of weight over him. Loose talk, a bad suggestion over drinks, or expressing anger about somebody is not the same thing. The inducement must be the determining cause of the crime — meaning that without it, the one who acted would not have acted. This is why exactly what was said, by whom, and to whom, tends to decide these cases.
Indispensable cooperation: the 'without which' test
The third category is narrower than people assume, and the narrowing sits in the words without which it would not have been accomplished. Providing something the others could readily have got elsewhere is cooperation, but not the indispensable kind. Providing the only key, the only vehicle, the sole access code or the single means of entry is different, because the crime as actually committed depended on it. The question is measured against the offence that happened, not against some other way it might conceivably have been done.
The lesser roles still carry liability
Falling outside the three categories does not put you in the clear. The Code also recognises accomplices, who cooperate by prior or simultaneous acts that help but are not indispensable, and accessories, who come in after the fact by concealing the crime, profiting from it, or helping the offender escape. Both carry lighter penalties than a principal's, which is exactly why the classification is contested so hard. A complaint or information naming you as a principal is the prosecution's starting position, not a finding, and the role assigned to you can change as the evidence is tested.
Where planning alone leaves you
It depends on what the planning consisted of and what followed it. Under Article 8, conspiracy exists when two or more persons come to an agreement concerning the commission of a felony and decide to commit it; for certain offences the agreement is itself punished even if nothing further happens. Where the plan is carried out, someone who agreed to it may answer for the result although he stayed away. If you are being asked to give a statement about a meeting you attended, speak to a lawyer before you say anything about it. Accounts offered to sound harmless are often what supplies the missing element.