It took jurors less than 4 hours to deliver a guilty verdict Wednesday against Magdelena Luczak and Mariusz Krezolek, who are originally from Poland but reside in Coventry, England, The Belfast Telegraph reported.
Daniel died on March 1, 2012, after suffering a severe head injury.
Prosecutors said the couple starved the Daniel, kept him locked in a small room, and force-fed him salt. He was also beaten and made to perform strenuous exercises as punishment.
Luczak and Krezolek told the boy's teachers he suffered from a rare genetic condition that caused him to lose weight.
The couple face a mandatory life sentence for their convictions. They are to be sentenced Friday.
British Deputy Prime Minister Nick Clegg said society is partially responsible for Daniel's death, The Guardian reported.
"Clearly people must have seen something was wrong with this boy. I think his death should be on all of our consciences," Clegg said. "We all ask the same questions. How did this happen? What happened when teachers saw this boy scavenging in bins, when they saw him lose all that weight? They apparently did pass information on. Why did no one act on it? When he went to hospital and the mum and stepfather spun a web of lies, what happened to the concerns people had?"
Coventry's Safeguarding Children Board is looking into the incident, including why social services and police didn't become involved after seeing bruises on the boy.