The child welfare investigator who resigned under fire after an 11-month-old Kendall boy was left to die in a sweltering car by his mom had a history of sloppy paperwork and slipshod investigations, Department of Children and Families administrators said Thursday.

But the head of the oft-criticized agency, David Wilkins, insisted the investigator’s failures were an aberration, not a sign of systemwide dysfunction.

Since the death of Bryan Osceola on May 16, DCF has been rooting through the case files of Shani Smith. Months earlier, the investigator had deemed it unnecessary to take steps to protect Bryan after an incident in which his drunk mother fell asleep behind the wheel of her car, with the unsecured Bryan sprawled in the front seat. The car was still in drive.

As child welfare bosses struggled to explain the latest death of a child on DCF’s radar, members of the Community-Based Care Alliance, a Miami oversight board, wanted to know what the state was doing to prevent future tragedies.

Some were skeptical that the problems at DCF are limited to one investigator.

Miami-Dade Circuit Judge Jeri Beth Cohen. who chairs the group, said that Smith “was obviously a liar and extremely unethical,” but that proper supervision was lacking as well.

“This is not just one instance; it’s a systemic problem,” she said.

Bryan was 5 months old last November when Catalina Marista Bruno was found passed out behind the wheel with her car in drive at midnight in the vicinity of Krome Avenue. The unsecured child was next to her in the front seat.

Despite the subsequent DUI arrest, Smith determined that Bruno did not have a drinking program. She cited the opinion of an unnamed substance abuse evaluator. DCF now believes the opinion was never solicited and that Smith concocted the consultation.

On May 16, prosecutors say, Bruno left Bryan to die in a hot car, alongside her purse and a can of beer, a death that has triggered one of the DCF scandals of the past few years.

A review of Smith’s 113 cases by DCF investigators showed that Smith had performed “minimal investigative activity” on a disturbing number of them, had poorly assessed the risk to many children — or had completed no risk assessment at all — and had a higher average than her counterparts across the state of finding no evidence that children had been abused or neglected.

Of the 113, 30 percent are requiring some kind of “corrective action,” DCF’s top Miami administrator, Esther Jacobo, told the alliance. That 30 percent included 28 files that had to be revised to reflect some concern that a child was at risk. Thirteen cases required the agency to visit youngsters who were previously believed to be risk-free, “to determine if the children were safe and whether the families needed services,” Jacobo said.

Wilkins, who also appeared before the oversight board, said: “When things go wrong, we have to figure out what went wrong and do our best to improve it.”

Wilkins recalled coming to Miami two years earlier to explain to community leaders how another child had died despite being on the agency’s radar screen on multiple occasions.

In the case of Nubia Barahona, whose adoptive parents are facing murder charges, the failures were system-wide, including lapses in investigation, supervision, the court system, and foster care and adoption case managers, Jacobo acknowledged.