The answer
The definition of a Christian martyr is one who dies for the sake of his/her faith that Christ Jesus is indeed God Incarnate and One in the Holy Trinity with the Father and the Holy Spirit.
1) To be considered a Christian martyr, one would have to be a believer (Matthew 5:11,12).
2) If a Christian dies naturally, he/she would not be considered a martyr, but perhaps may be considered a confessor or a righteous person, depending upon the circumstances.
3) Every person should be prepared by living a life of repentance through the Holy Sacraments, in addition to expressing brotherly love and charity towards others. If one chooses to not live his/her life in this manner, then, in essence, one is choosing his/her destiny.
4) Only God knows the depth of one's heart and will judge each person according to His mercy and His justice.
Answered by His Eminence Metropolitan Youssef (opens in a new tab)