# Using the Cosine Effect as a Defense to a Radar Based Speeding Ticket

1. Junior Member
Join Date
May 2011
Posts
1

## Using the Cosine Effect as a Defense to a Radar Based Speeding Ticket

My question involves a speeding ticket from the State of: Washington .
I received a radar ticket from the following situation : The officer was at the crest, at the top of a 100' hill, and both cars were traveling. My car was on the flat, at the bottom. I know that the
"cosine effect set-up" from the radar can affect its accuracy. I know I was not speeding. What advice do you have for me, for court ?

2. Senior Member
Join Date
Sep 2010
Posts
6,658

## Re: Using the Cosine Effect as a Defense to a Radar Based Speeding Ticket

If you're going to mount this sort of defense, you better have an expert witness and advisably a lawyer.

It doesn't sound like the cosine effect has any bearing here. If I understand you correctly, you were travelling, relative to the police car, in the same direction the gun was pointed. The cosine error comes from when the cop is off to the side and you are moving at an angle to the radar "beam"

3. Senior Member
Join Date
Dec 2004
Location
Seattle
Posts
3,377

## Re: Using the Cosine Effect as a Defense to a Radar Based Speeding Ticket

Plus, you do understand that the "cosine effect" FAVORS the driver, right? I mean, if you are at a 45 degree angle, for example, and the officer "clocks" you at 70, that means you were ACTUALLY going 100! The cosine effect ONLY makes your car appear to be going SLOWER to the RADAR than it actually is -- NEVER FASTER!

Barry

4. jk
Senior Member
Join Date
Jan 2006
Posts
20,733

## Re: Using the Cosine Effect as a Defense to a Radar Based Speeding Ticket

Quoting blewis
Plus, you do understand that the "cosine effect" FAVORS the driver, right? I mean, if you are at a 45 degree angle, for example, and the officer "clocks" you at 70, that means you were ACTUALLY going 100! The cosine effect ONLY makes your car appear to be going SLOWER to the RADAR than it actually is -- NEVER FASTER!

Barry
I wonder if anybody has ever tried to utilize such a defense and ended up convincing the court they were guilty of (as an example) 100 when they were clocked and ticketed at 70.

5. Senior Member
Join Date
Dec 2004
Location
Seattle
Posts
3,377

## Re: Using the Cosine Effect as a Defense to a Radar Based Speeding Ticket

I watched a guy try to use the argument once, simply to prove that there WAS some error. WA's "speed trap" law has a provision that states that devices are "limited to devices or observations with a maximum error of not to exceed five percent using the lapsed time during which such vehicle travels between such limits." He argued that the cosine effect produced an error greater than 5% in his situation. The judge pointed out that RADAR does NOT use the "lapsed time" method of calculating speed -- GUILTY!

Barry

1.

#### Posting Permissions

• You may not post new threads
• You may not post replies
• You may not post attachments
• You may not edit your posts
•