Samsung Electronics tried to impose an "unfair and unreasonable" royalty rate on Apple Inc for the use of its wireless patents in the iPhone, which would have stymied Apple's commercial prospects, a former Texas Instruments lawyer said on Friday.

Richard Donaldson, who retired as the chipmaker's lead patents attorney, told the court he viewed a 2.4-percent royalty Samsung wanted on the price of the iPhone as discriminatory, because those patents enabled just a fraction of the smartphone's features.

Samsung accuses Apple of infringing those patents, which are related to wireless communications for smartphones and are broadly licensed to Intel Corp and other technology corporations.

Apple accuses Samsung of copying the design and some features of its iPadand iPhone.

The former Texas Instruments executive joined a string of rebuttal expert witnesses Apple presented in court in the closing hours of its U.S. legal battle with its Korean rival, one facet of a bigger war for mobile industry supremacy between two corporations that sell more than half the world's smartphones.

"If other companies were to determine that this is a reasonable royalty, then the total royalty on the iPhone would be something like 50 percent," Donaldson testified.

"It's neither fair nor reasonable because you could not be successful in the market."

Other expert witnesses included Michael Walker, a former senior Vodafone research executive who from 2008 to 2011 chaired the European telecoms standards authority, who said Samsung failed to disclose in a timely fashion the same patents to which Donaldson referred.

Friday's testimony centered on the concept of standards or essential patents, which are intellectual property built into a commonly agreed set of specifications -- in this case, the UMTS wireless communications standard widely used around the world by mobile devices.

Apple's lawyers argue that Samsung, a part of the body that crafted and adopted UMTS, is charging an unfairly high licensing fee on those patents, in effect trying to stymie its market advances. Samsung has said those patents were its intellectual property, for which it rightly requires compensation.

On Friday, Samsung's lawyers did not cross-examine many of Apple's witnesses at length because the Korean company had used up almost all of its allotted trial time of 25 hours, giving Apple major leeway in directing their witnesses.

The case in U.S. District Court, Northern District of California, is Apple Inc v. Samsung Electronics Co Ltd et al, No. 11-1846.