A forensic pathologist who has reviewed official reports relating to the death of Lennon Lacy, the black teenager who was found hanging from a noose in North Carolina, has questioned procedures followed by local and state authorities and challenged the official determination of suicide.

Dr Christena Roberts, a Florida-based specialist in crime scene pathology, was brought in by the North Carolina branch of the National Association for the Advancement of Colored People (NAACP), which has been advising Lacy’s family as they try to get to the bottom of what happened to the 17-year-old high school student and football player. He was found hanging from a swing set in a largely white trailer park in Bladenboro, a small town in the south of the state, on the morning of 29 August, just hours before a big game in his school’s football calendar.

An official autopsy carried out by the chief medical examiner, Dr Deborah Radisch, soon after Lacy’s body was discovered concluded that the cause of death was “asphyxia due to hanging”. But both the medical examiner investigation report and the death certificate went further, listing the manner of death as “suicide”.

Roberts reviewed all these stages in the official investigation on behalf of the NAACP, and met with the medical examiner. In her findings, she raises several concerns about the procedures that were followed and the conclusions that were reached.

The pathologist does not give any firm answers to the mystery of how Lacy died – whether it was self-inflicted or involved foul play. But she does suggest that the official parties may have been hasty in giving a firm indication that this was a suicide.

The Lacy family, led by Lennon’s mother Claudia and brother Pierre, have been distressed by how quickly the authorities formed the opinion that the teenager killed himself. They are demanding a more thorough inquiry, which would take into account any racial tensions in the area. With the support of the NAACP they have called on the US Department of Justice and FBI to get involved.

Roberts begins her report by questioning the emphasis made in official accounts, including the autopsy, on Lennon Lacy having been “depressed” after the death of his great uncle, with whom he was close. Roberts points out that Lacy gave no indication he had thought about taking his own life, such as expressing a desire to hurt himself, making preparations to give away his prized possessions or leaving a suicide note.

At the location where Lacy’s body was found, hanging from one of a series of swing sets in the middle of a square of trailer homes, Roberts also found puzzling features that were not reflected in the autopsy or other official reports.

She writes: “There was no item present at the scene that Lennon could have stood on, applied the noose then kicked away.”

The noose, which was fashioned out of two belts, did not appear to Roberts to be long enough for Lacy to have got his head through from the position on the swing set at which he would have had to be standing. The pathologist was also bemused by the fact that when Lacy’s body was placed in a body bag he was wearing white sneakers that were two sizes too small for him, shoes which were nowhere to be seen by the time the body arrived at the medical examiner’s office.

“It is not the usual practice for the police to remove clothing from the body before transport,” Roberts says.

Roberts’ findings do agree with the autopsy report in some important regards. She says fears Lacy’s face showed a large bump on the right forehead could be discounted, given photos taken at the autopsy in which no such contusion was visible. She also agrees that marks on his face were due to ant bites.