The phrase "assembling a case" is correct and usable in written English.
It can be used in contexts related to law, research, or any situation where evidence or arguments are being gathered to support a particular position or conclusion.
Example: "The lawyer spent weeks assembling a case to present in court, ensuring that all evidence was meticulously organized."
Alternatives: "building a case" or "preparing a case".
Days after their visit, prosecutors began assembling a case that would become known throughout the world as the Minova trial.
In my mind, I made a frenzied inventory of Dale's defects — as though assembling a case to rebut an aggressive prosecutor.
Now, nearly a century after Casement's execution, Vargas Llosa has attempted to appease his uneasy ghost, assembling a case for his reprieve.
"How can I do anything if I don't know?" Father Manship said he and the merchants had been assembling a case to document their stories, and videotaping police action.
The prosecution probably would try to limit how much it relies on the documentary to keep Durst's defense team from raising doubts about the film's accuracy and from challenging the unusual role the filmmakers played in assembling a case against Durst, the experts said.
The dataset was collected from Ref. [11] by Bearman, Faris and Moody [12] who used it to propose a network aided method of assembling a case from heterogeneous interview data (rather than studying social memory processes).
The government assembled a case so strong that Dr. Chang's lawyers could hardly offer a defense in opening statements.
The American official familiar with the Al Majalah incident said that U.S. and Yemeni officials had worked together to assemble a case against Shaea.
Detective Smith said Salvadorans With Pride had been targeted first because informants had allowed investigators to assemble a case more quickly than with other gangs.
Britain's police already have longer than most to assemble a case, and an impressive array of those who should know oppose the extension (see article).
Indeed, prosecutors have assembled a case that appears to depend not so much on the specific effect of any one accusation but instead on the overall impact of a range of activities over many years.
