Three of those patients have since died, but at a press conference on Thursday in Stockholm, prosecutor Jennie Nordin said that Macchiarini is no longer a suspect.
“Paolo Macchiarini has acted negligently and it was wrong to do this,” Nordin said of the three operations involving implanting synthetic tracheas.
However, while those operations were negligently carried out, Nordin said, she and the other prosecutors were unable to prove that any crimes were committed - as she explained through a translator:
“No crime was committed because we cannot show that a better outcome would have happened if alternative methods would have been used.”
Macchiarini has performed similar surgeries on several patients around the world, but the Swedish prosecutors have not considered those cases, Nordin said, beyond looking at the journal of one patient in the US.
“We requested and received the patient journals of Hannah Warren in the United States. We obviously had access to publicly available information and we've come into some contact with the patients within the framework of the interviews carried out, but nothing more than that.”
Macchiarini was informed on Thursday morning of the fact that the prosecutors will not press charges against him, but Nordin said she does not know where Macchiarini is right now or what he does today.
Macchiarini's Swedish lawyer Björn Hurtig said his client was pleased that the investigation has been closed, even if both Macchiarini and Hurtig were surprised, he said, about the prosecutor's claim that the surgeon acted in a negligent manner.
"At the same time, they say that they cannot account for any other method that would have been better and so neither I nor Paolo (Macchiarini) understand why he should have acted negligently," Hurtig told news agency TT.
While the team of prosecutors led by Nordin have cleared Macchiarini, persons with connection to the case can appeal their decision.
Macchiarini's synthetic organ transplants were first considered a groundbreaking medical procedure but in the end led to what has been described as one of the biggest medical scandals in modern times in Sweden.
On Thursday afternoon, Sweden’s minister for higher education and research, Helene Hellmark Knutsson, said that she wants to see harsher punishments for research fraud.
“What has happened is truly awful and we are reminded of the suffering that the patients were subjected to. As regards the punishment, it is a good thing that this has been properly investigated, but at the same time the potential breaches of ethical reviews could not be tried due to the short statute of limitations,” Knutsson told TT.
“It is incredibly important that we have trust in research and that ethical reviews are carried out. No patient should be subjected to experiments,” Knutsson added.
Nordin said that the debate and media attention surrounding the surgeon did not directly influence her investigation.
"We were of course aware of the debate," Nordin said, "but we considered this matter through the lens of criminal law."
Nordin said she believes health-care professionals should continue the debate regarding when and in what way it is admissable to take measures that are deemed to be potentially life-saving.