A former Apple designer has backed up the company's claims that Samsung gadgets look "confusingly similar".
Susan Kare, who from 1982 to 1986 had a hand in designing icons for the original Macintosh computers, scrutinised 11 of the Korean firm's phones – including the Galaxy S and Epic 4G – and found icons and layouts on screens to be very similar.
Apple is contending that buyers may confuse Samsung devices with the iPhone, and accuses the Asian firm of copying designs and features.
Samsung, in turn, has accused Apple of violating Samsung wireless technology patents.
Kare – who is also credited for Microsoft icons such as the 'Notepad' and for its deck of 'Solitaire' game cards – testified that even she was fooled by a Samsung gadget at a pre-trial meeting.
"There was a big conference table with many phones on it, and some of them were on," said Kare, who followed the late Steve Jobs to his NeXt computer startup in 1986 before starting her own firm.
"I could see the screen. I went to pick up the iPhone to make a point about the user interface, and I was holding a Samsung.
"I think of myself as someone who's pretty granular about looking at graphics, and I mistook one for the other."
When it was Samsung's turn to cross-examine Kare, lead attorney Charles Verhoeven switched on a Samsung phone and asked Kare to tell the jury what she saw: a bright white Samsung logo.
In response to Kare's testimony that the icons looked largely similar, Verhoeven shot back: "Have you ever seen triangular icons?"
In an echo of testimony from earlier this week, when both sides laboriously noted similarities and differences between devices, Verhoeven painstakingly called attention to visual differences between common icons on the iPhone and Samsung's gadgets.
They included the short-messaging and calendar buttons.
Apple and Samsung are going toe-to-toe in a high-wattage patent dispute, mirroring a fierce battle for industry supremacy between two rivals that control more than half of worldwide smartphone sales.
The trial playing out in San Jose is just one of many disputes between the two around the world that analysts see as partly aimed at curbing the spread of Google's Android, the world's most used mobile software.
Testimony later this week will focus on the iPhone's familiar front face, with its outsized square icons, switching tack from the earlier meticulous review of uniform displays and bezels.
Kare pointed to numerous similarities on Samsung phones, including rounded corners, a range of icon styles from retro-plain to stylised, and an evenly spaced grid.
"It is my opinion that the overall collection of graphic features that makes the overall visual impression could be confusing to a consumer," Kare told the packed courtroom.
Research in Motion's BlackBerry Torch was held up as an example of how smartphone displays might be differentiated.
"You can do a design without having it be confusingly similar," she said.
The trial has granted Silicon Valley an unprecedented peek behind the curtain of Apple's famously secretive design and marketing machine, and unearthed internal Samsung documents in which the Korean company saw the iPhone as a competitive threat and sought to match it.
Apple's lawyers earlier this week brought on marketing expert and New York University lecturer Russell Winer to discuss the value of Apple's brand as embodied in the iPhone and iPad, which reinvigorated a then-moribund tablet computer market in 2010.
Samsung "viewed the iPad as a target, one to be emulated, and one to be studied carefully for future refinement", he said.
Winer then read from an internal Samsung document – one of many that Apple's camp has produced in past days.
"People don't think [the industrial designs] of Samsung touchphones are groundbreaking," according to the document. "Nothing stands out as something consumers have never seen," Winer recited.
He stopped short of saying Samsung might have actually intended to copy Apple products.
Samsung strategy chief Justin Denison has said executives sometimes resort to hyperbole internally to motivate and energise their troops, and that any comments upholding the Apple model might be construed as such.
Apple has ceded pole position in smartphones but remains the leader in tablets, holding fast to its lead as rival products from Motorola, Research in Motion, Hewlett Packard and others have fizzled out.
But Samsung is gaining ground.
Speculation has mounted that Apple plans to make a mini-iPad to take on cheaper gadgets from its Korean rival, as well as from Google and Amazon.
Last week lawyers showed Apple vice president Eddy Cue, in a January 2011 email, urging then-chief operating officer Tim Cook to build a mini-iPad because he believed there was a market for a 7in tablet.
Late co-founder Steve Jobs was receptive to the idea, according to Cue's email.