The date of a positive COVID test Novak Djokovic used to enter Australia has been called into question by a BBC investigation which analysed the serial numbers of test results he submitted to the Federal Court. 

The world number one tennis player was deported earlier this month after the Federal Court rejected his bid to overturn a federal government decision to cancel his visa.

Djokovic's initial medical exemption was granted on the basis he tested positive on December 16, 2021.

Among documents Djokovic's lawyers filed to the Federal Court were two COVID-19 tests — one which indicated he had tested positive on December 16, 2021, and one which showed he had tested negative on December 22, 2021. 

The documents submitted to the Federal Court included a confirmation from the acting director of Serbia's health body confirming the accuracy of the dates on the certificates.  

However, the BBC investigation found Djokovic's two tests were out of sequence, as the serial number for the later test (7320919) was lower than the earlier test (7371999).

Examining 56 COVID-19 tests they had gathered from Serbia, the BBC found that all the codes fit in the same chronological order, except for Djokovic's December 16 positive test.

According to their analysis, the serial number of Djokovic's positive test fit chronologically in between tests dated December 25 and December 28. The BBC said this suggested his positive test result may have actually occurred sometime between these two dates.

The BBC said it had put its findings to Serbia government officials on multiple occasions but had not received a response.

Djokovic's team had also not responded to interview requests.

In an attempt to explain the code discrepancies, an expert approached by the BBC said it was possibly the result of a technical glitch. But he said he was unsure why state authorities would not be forthcoming with such a reason.

The possibility that different labs may have different batch numbers was also suggested. But later test results processed in the same lab as Djokovic's positive test were found to have lower confirmation codes. 

Djokovic was photographed attending public events maskless on December 16, the same date the documents said he tested positive. Djokovic arrived in Australia on January 5. 

Djokovic at risk of missing French Open

Djokovic is at risk of missing the French Open after France tightened its vaccination rules for sports events.

From February 15, anyone who is not vaccinated against the coronavirus will need to show proof they tested positive for COVID-19 within the previous four months — down from the current six-month window — in order to enter sports venues in France.

The French law is central to the government's plan for tackling the virus and aims to bar unvaccinated individuals from stadiums, restaurants, bars and other public places.

Under the current rules with a six-month window, Djokovic could play in the French Open, which starts May 22.

But if the new requirements stay in force until then, they are likely to rule him out unless he gets vaccinated or tests positive again within four months of the start of the clay-court Grand Slam.

The top-ranked Djokovic is the defending champion in Paris. 

French Open organisers have previously said it's too early to comment since virus restrictions can change between now and May depending on the situation.

ABC/wires