The phrase "supposed cause" is correct and usable in written English.
You can use it when referring to an assumed or suggested cause of something, such as: We must study the supposed cause of the epidemic before we can find a cure.
But more often it's not pranksters who slash art but self-promoters with a supposed cause.
One shows an American pathologist in 1955 stealing Albert Einstein's brain in the supposed cause of scientific advancement.
For the person who resorts to random killing in order to promote the honour of God or the supposed cause of justice, it is clear that God is not to be trusted.
The supposed cause of our new racial uproar, the senator's remarks at Strom Thurmond's centennial birthday party, rapidly became irrelevant to the big picture (as did the clueless majority leader himself).
On the magazine cover, each crease in his face is labeled with a supposed cause: the sanitation strike, the Tombs riots, the presidential debacle, the school strike, the transit strike, the long, hot summer, and on and on.
Take the proverbial back of a cereal box, divide it into six rectangles, and on each one, write a supposed cause of the political turbulence now gripping the west: "the financial crash of 2008", "inequality", "racism and xenophobia", "Tony Blair, basically", and all the rest.
But when Levitt turned an economist's eye to the data, he found that most of the supposed causes -- innovative policing strategies, stricter gun control, a strong economy, the aging of the population -- had a negligible effect.
It goes out of its way to list and then to debunk all the supposed causes, from violent video games to the punishing social hierarchy of high school life.
Although stressors are generally studied separately, we simultaneously measured several variables directly or indirectly reflecting the supposed causes of bat decline: availability of woodland habitats around bat roosts, genetic differentiation amongst colonies, and exposure to chemical pollutants and to a protozoan parasite, Eimeria hessei.
This entire narrative of a retiree bankruptcy boom and its supposed causes falls apart as soon as you start pulling at the strings.
Dr Jose Bartolache was convinced that the cacao plant played a major role in ill health, although very tight clothes and going to bed late were other supposed causes.
