Scientifically death is cessation of blood circulation and breathing, which are the two most essential criteria to sustain human life. Brain activity stops within 20 to 40 seconds after death.
The building blocks of organisms namely cells, tissues, organs and systems have to die or shut down before the organism is scientifically declared as dead. Brain activity stops almost immediately. This does not include violent death like decapitation and the like
Doctors have recently found scientific evidence that the brain can continue to work after the patient has died. A patient showed a continuous brain activity for 10 minutes after his heart stopped, and doctors recorded brain waves from those normally obtained during deep sleep. Doctors described the case as "unusual, unexplained.
Absence of pulse confirm death which is due to heart and lungs. All organs are under the control of brain. It means that brain is no more I unctional after death