Channel 4 will air footage not seen before and “significant evidence” about the death of Stuart Lubbock at Michael Barrymore’s house and the murder of Peter Falconio in Australia as the broadcaster announced a series of shows for 2020 intended to ensure the broadcaster is youthful and provocative.

Ian Katz, the director of programmes, said the broadcaster’s “centre of gravity” and complexion of its programming is changing after it successfully argued against the government’s attempts to make it relocate its entire operation out of London, instead opening a national headquarters in Leeds and offices in Bristol and Glasgow.

Speaking in London at the launch of Channel 4’s new shows, Katz explained the decision to look again at the crimes, which took place in 2001.

“In both cases we have unearthed significant evidence that raises questions about the generally held understanding of those events,” he said.

“In the case of Joanne Lees and Falconio there have been a string of stories over the years saying was the right guy convicted. This is the most substantial investigation I think there has been of the case and I think will raise real questions about it.”

The Lubbock documentary, Unexplained, has been made with the cooperation of his family and broadcasts for the first time the 999 call made after his death in Barrymore’s swimming pool in Essex.

Katz said: “It’s extraordinary that 19 years after Stuart Lubbock was found everyone knows that something terrible happened there and no one’s been held accountable … I think this show moves some way towards answering that gap.”

Terry Lubbock, Stuart’s father, said: “The story has become so distorted and confused over the years. So much has been said and written. It’s time to put all the facts together in one place.”

Also this year Channel 4 will follow up its 100 Vaginas series with a “provocative look at 21st-century masculinity” in a candidly titled programme called Penises, and it will examine women’s changing attitudes to pubic hair in Bring Back the Bush.

Other provocative shows include the Segregation Experiment – a programme that follows a school’s tests for unconscious bias in children in ways that include segregating them, and a satirical look at Prince Harry and Meghan’s plan to step down as senior royals in the return of the comedy The Windsors.

Additional highlights include Write Offs – a series about illiteracy hosted by Sandi Toksvig culminating in a spelling bee – Channel 4’s move into natural history with Living Wild and comedies including Amy Poehler’s co-creation Duncanville and the comedy series Maxxx on new youth channel E4.

Channel 4’s chief executive, Alex Mahon, said it was important to focus on attracting more younger viewers because “their behaviours are changing faster than older viewers, they go more to streaming”, but said “we still want to be broad” and appeal to older audiences.

Mahon pointed out that last year Channel 4 aired 24 of the 30 top-rating youth shows, and also its ethnic minority audiences were up 9% – a record.

Katz said the broadcaster’s new regional bases were helping to change its makeup, with some ideas not being commissioned because the new regional commissioners were telling him that “no one outside London is interested in that”. He said the less metropolitan feel would become more apparent when the BBC Breakfast presenter Steph McGovern begins her new daily current affairs show in the spring.

The Channel 4 bosses appeared confident that the broadcaster can continue to challenge convention despite clashing with the government last year over its decision to fill Boris Johnson’s empty place in its climate change debate with an ice sculpture and after Johnson was called a “known liar” by Channel 4’s head of news and current affairs, Dorothy Byrne.

Mahon noted that the government’s threat to its remit made during the general election had been withdrawn and said: “Elections are a heated time. On the climate change debate, Ofcom gave us a very clean bill of health on impartiality.”

Meanwhile, Katz said after the success of Brexit: The Uncivil War, which starred Benedict Cumberbatch as Johnson’s adviser Dominic Cummings, “we are working on a number of projects with James Graham who wrote that show”, but whether Cummings will be in them or not “is another question”.