"I find it extremely odd that the authorities could sit on a case for nearly three years, and then within two weeks find "new" evidence to suddenly sentence a man to death", said William Nee, China researcher for Amnesty International.
Though Meng was released on bail a few weeks ago, she remains on house-arrest in British Columbia while the U.S. pursues her extradition, as Chinese authorities have responded furiously to her detainment and have threatened consequences.
The Canadian, who is believed to be 36, was arrested in 2014 and accused of planning to smuggle nearly 500lb (227kg) of methamphetamine from China to Australia.
The Dalian court's verdict reverses the earlier sentencing in November of the Canadian national to a 15-year jail term.
There are also cases pending against two other Canadians arrested in China on charges of "endangering national security".
Experts said retrials are rare in China, especially ones calling for a harsher sentence, but rights groups noted that courts are not independent and can be influenced by the Communist Party.
Last week, Trudeau accused China of "arbitrarily and unfairly" detaining former diplomat Michael Kovrig and business consultant Michael Spavor, who were rounded up 9 days after Canada arrested Huawei executive Meng Wanzhou.
Zhang said there was insufficient evidence to prove Schellenberg was part of a drug syndicate, or that he was involved in the smuggling of methamphetamines. "The announcement of the sentencing was all very fast, it took around 20 minutes", said Schellenberg's lawyer Zhang Dongshuo, according to the South China Morning Post.
In the weeks that followed her arrest China detained two other Canadian citizens.
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"The evidence against Schellenberg is "...compelling and ample, and the criminal charges are well founded", the court said. The man was sentenced on Monday for smuggling more than 200 kilograms of drugs to death.
Canada's prime minister Justin Trudeau has accused Beijing of arbitrarily applying the death penalty in Schellenberg's case.
China's Foreign Ministry spokeswoman Hua Chunying expressed "strong dissatisfaction" with Trudeau's remarks in the latest back-and-forth between the two countries, Reuters reported.
An editorial in the nationalist state-backed Chinese newspaper Global Timeson Tuesday said "unreasonable speculation" in Western media linking his case to Ms Meng's showed "rude contempt toward Chinese law".
He added that Canada would "continue to talk to our allies and to China about this".
"We have seen before that in highly politicized cases the trial is often a mere spectacle with the outcome already decided".
The execution by Chinese authorities of a British citizen in 2009 on drug trafficking charges stoked worldwide controversy and condemnation from Western countries.
"I think people around the world are horrified by this case because it's such an incredibly crass, politicized and really grotesque response to a diplomatic spat", she told CTV News Channel.
"It's hard not to see a link" between the case and Canada's arrest of Meng, Saint-Jacques said.