Please clarify in detail how a specific person can be judged as a heretical innovator.

All perfect praise be to Allaah, The Lord of the Worlds.  I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

There are certain criteria that must be fulfilled when making judgments about others and saying that a particular person is, for instance, a heretical innovator. The following are these criteria:

First, in principle, the Muslim is innocent and honest unless proven by Sharee‘ah-approved evidence to be otherwise. In fact, no judgment must be made without sufficient proof.

Second, when the Quran and Sunnah indicate that a particular saying or act implies a certain judgment.

Third, when someone does a specific action or says a particular word and meets certain conditions, such as the following: knowledge, freedom of choice, lack of misunderstanding and misinterpretation. If these conditions are met, then the impediments like ignorance, coercion, and misunderstanding will also be missed and he will be judged as a disbeliever or a heretical innovator.

Shaykh Al-Islam Ibn Taymiyyah mentioned that when a person commits any religious innovation or anything that is prohibited by the Quran and Sunnah or anything that contradicts them, he might be excused for one reason or another. For example, he may have made a mistake in his personal reasoning or in his imitation of reliable scholars for which he deserves to be excused. Likewise, perhaps the person is unable to understand things correctly. He added that a person is not to be judged as a disbelieving  innovator or a disbeliever unless certain conditions are met and certain impediments are absent. For instance, performing Jihaad against disbelievers should be preceded by calling them to Islam as there is no punishment for those who have not learnt about the message of the Prophet, sallallaahu ‘alayhi wa sallam. Moreover, disobedient people  are not to be punished until they have been informed beyond the excuse of ignorance and doubt.

Allaah Knows best.