The verdict, which came more than five years after Mr Lotter was shot dead while travelling in a taxi in the Masaki district of Dar es Salaam, is being described as a significant win in the fight against animal poaching in the East African nation.
Mr Lotter was the co-founder of Pams Foundation, a non-profit that supports anti-poaching initiatives across Africa by providing expertise and help to communities and governments.
At the time of his death, he had been a leading conservationist and central figure in East Africa’s fight against poaching, partially responsible for some of the biggest ivory busts in the continent's history.
In 2015, with Mr Lotter’s help, Tanzania’s elite anti-poaching National and Transnational Serious Crimes Investigation Unit arrested Yang Feng Glan, a Chinese citizen, who led one of the biggest ivory syndicates in East Africa.
Yang, who was called the Queen of Ivory, is serving a 15-year sentence for trafficking 860 elephant tusks worth more than $6 million.
Between 2009 and 2014, ivory poachers decimated Tanzania’s elephant population, reducing it by more than 60 per cent.
Before his killing, Mr Lotter had received multiple death threats for the work he and his organisation were carrying out, the Pams Foundation said.
Since 2012, the NTSCIU has arrested nearly 3,000 poachers and ivory traffickers leading to prison sentences over 90 per cent of the time.
It took investigators years to build their cases against the 11 people convicted in Mr Lotter's murder, who include the two gunmen and nine accomplices.
“It really feels like we finally achieved our milestone that we've been plugging away at for so long,” said Krissie Clark, executive director of Pams Foundation, who co-founded the organisation with Mr Lotter. “It just feels amazing to be able to close this chapter.
While the 11 were given death sentences, that equates to life in prison, as Tanzania has not carried out an execution since 1995, Pams Foundation said.
The case took half a decade to wind its way through the Tanzanian justice system, with multiple attempts to derail it, explained Mary Rice, Executive Director of the Environmental Investigation Agency.
Ms Rice described Mr Lotter’s death as “well planned” and a “co-ordinated assassination.”
"Someone who was threatened by the success of Wayne and Krissie’s efforts to address organised poaching and ivory trafficking networks that had been operating out of Tanzania for so long. Someone with influence, protection and financial backing."
She credited the Tanzanian government with seeing the case through.
“That Tanzania has recognised this and has ensured the case was followed through with due process demonstrates a positive step in the fight against the corruption that plagues so many similar cases,” she told The National.
Ms Clark, who was in the car with Mr Lotter when he was murdered, said the last five years had been “challenging” and that she was looking forward to “moving on” and continuing Mr Lotter’s life work.
“He was an incredible guy with dedication, passion and integrity,” she told The National. “If everyone could work with the same passion, dedication and determination as he did, this [world] would be an incredible place.”
In her sentencing, Judge Edith Mgonya said “[Wayne’s] death did not only affect his family, his foundation and his friends but Tanzania as a destination and the world at large.”