Three-day-old Michael — who police call a child of incest and abuse — had an undignified funeral: His little body was tossed into a furnace in the dark cellar where he and his three siblings had been imprisoned along with their mother for their entire lives.
Police say the infant was one of seven children Austrian Josef Fritzl told them he fathered through incest with his own daughter. Michael's death is now the centerpiece of the trial of the man who imprisoned his daughter for 24 years and repeatedly raped and tortured her. Among the issues still to be decided, is if any of the surviving children will take the stand.
Three of Michael's surviving siblings were confined to the dungeon-like bunker while three others lived as a second family upstairs with Fritzl and his wife.
Prosecutors are investigating to determine whether Fritzl murdered the baby in the basement of his home in the quiet village of Amstetten, Austria. If convicted, Fritzl himself could be locked away for life.
Gerhard Sedlacek, spokesman for the prosecution, told ABCNews.com that his team has hired a "child death specialist" who is preparing an expert opinion. He said conditions in the windowless basement may have contributed to the death of the baby.
The expert witness — a neonatologist — was present during the testimony of Fritzl's 42-year-old daughter Elisabeth, Michael's mother, who so far is the only family member to accuse her father of torture.
The medical expert's opinion will help prosecutors decide whether Fritzl will be charged with manslaughter. If he is found guilty in the infant's death, he could face a life sentence. Without that charge, he is likely to serve only 10 to 15 years.
"If it emerges that Fritzl was aware that the child was severely ill and he did nothing to get medical help, that would be a case of murder under negligence and he would be charged accordingly," said Sedlacek.
Fritzl, 73 and a retired engineer, has admitted that he burned the tiny body, but has apparently denied any responsibility for the baby's death. Authorities say DNA tests confirm he is the father of all Elisabeth's seven children.
European press reports say he has already made a partial confession and is also being charged with rape, abuse, deprivation of freedom and incest.
According to the prosecution, Elisabeth was interviewed in a secret location after medical experts pronounced her in good health.
All family members, including Elisabeth's mother and all her children, have been treated at a psychiatric clinic and guarded by police since Fritzl released his captives in late April after the oldest daughter, 19-year-old Kerstin, became seriously ill and was hospitalized.
When her two imprisoned siblings — Stefan, 18, and Felix, 5 — emerged from the dark cell, their immune systems were impaired due to vitamin deficiencies.
Kerstin was hospitalized for weeks with kidney failure and the entire family showed stooped posture due to the low ceilings in their underground enclosure.
The other three siblings, Lisa, 15, Monika, 14, and Alexander, 12, lived with Fritzl and his wife Rosemarie, 68, in the family home above the basement lair.
Next week, the prosecution will ask Kerstin and Stefan whether they will testify against their father, according to Sedlacek.