NEW YORK (CNNMoney.com) - The U.S. Patent and Trademark Office has issued the first final rejection on one the patents involved in the longstanding dispute between BlackBerry maker Research in Motion and patent holding company NTP.

A final rejection notice for one of five patents at the center of the case was mailed Wednesday, according to a posting on the Patent Office's Web site.

Shares of Research in Motion (down $1.11 to $73.04, Research) fell more than 1 percent in afternoon trading..

It is the first final rejection to be issued in connection with the BlackBerry patent dispute. The Patent Office is expected to eventually issue final rejections on the remaining patents involved in the suit, which could deny the validity of the patents and discredit NTP's claims.

NTP can still appeal the PTO's final rejection through the agency's appeals board.

The rejection comes ahead of a hearing Friday, when Judge James Spencer will decide in a district trial court in Richmond, Virginia whether or not to shutdown BlackBerry operations in the U.S.

Judge Spencer has said he sees the patent reexamination as a separate process from the legal proceedings. But experts say that since the Patent Office appears to be speeding up its review process, he may rethink the issue.

The legal dispute between RIM and NTP has dragged on for nearly five years. NTP successfully sued RIM for patent infringement and a jury awarded it damages. The district court issued an injunction stopping BlackBerry service. However, that injunction was stayed until RIM could appeal the decision.

An appeals court largely upheld that ruling. The case was then remanded back to the district court to make a final decision about whether or not to enforce the injunction and halt BlackBerry service. The hearing on that question comes this Friday.