The phrase "a major suspect" is correct and usable in written English.
It can be used in contexts related to crime, investigations, or discussions about individuals who are considered likely to be involved in wrongdoing.
Example: "After reviewing the evidence, the detective identified him as a major suspect in the robbery case."
Alternatives: "a primary suspect" or "a key suspect".
"He is certainly a major suspect.
The police have him down as a major suspect but he knows the truth.
The sanctions were suspended, but not lifted, in 1999 after Libya turned over a major suspect in the case.
They had briefed a local fugitive-apprehension team that morning, telling them that a major suspect would be passing through the airport.
Russian media have reported that Ruslan Geremeyev, a Chechen close to figures around Putin's man in Chechnya, Ramzan Kadyrov, was a major suspect.
On Monday, they detained his daughter as a "major suspect involved in the case", Xinhua reported, without revealing details about her role in it.
"Jamaica's delay in processing the U.S. extradition request for a major suspected drug and firearms trafficker with reported ties to the ruling party highlights the potential depth of corruption in the government," said a State Department counternarcotics report released in March.
Mrs. Hiett was not only the wife of the military officer who oversaw the Army's entire antidrug campaign in Colombia, but also the major suspect in a heroin-smuggling case in which drugs were being sent via diplomatic mail from Colombia to Manhattan and Queens.
The agents contended that he had held telephone conversations with a major drug suspect, Giuseppe Ganci, Mr. Badalamenti recalled.
The verdict appeared to add to the political risk by demonstrating that a jury could completely acquit a major terrorism suspect, despite Mr. Holder's vow that "failure is not an option" in the Sept. 11 case.
The report found that most of the 471 officers did not work weekends, when most of the calls for help occurred, and that crime-fighting units were so disorganized that one narcotics unit once descended with force on a major drug suspect only to find that another squad had gotten there first.
