Who becomes the main suspect in king Duncan's murder?

He was murdered in the castile of Macbeth the ... so they are considered to be the man subject of hi murder

The servants: Macbeth made the crime scene look like they killed King Duncan before he killed them. The King’s sons, Lennox and Malcolm: They had recently fled the country because they felt unsafe, which aroused suspicion about the possibility that they paid someone to kill their father. Macbeth: The Old Man suspected Macbeth because he had motive to kill and become King.

There are also a few more people who could have committed the murder for one reason or another, although they are not prime suspects. They are:

Macduff: Could become King if he killed King Duncan and Macbeth. Porter: He was drunk and wouldn’t have known what he was doing