UW: Give us a brief overview of your firm. You've been involved in several high-profile cases before, correct?
GR: Ralston & Associates is an environmental consulting firm specializing in water-related services. We conduct water quality and sediment sampling, hydrographic surveys, and fish and aquatic organism investigations.
We have volunteered our equipment and manpower for water search and rescue activities since 1982. In 2001 we purchased a sidescan sonar system for use in our business, but it has been primarily used for searching for drowning victims and other objects underwater.
In 2002, we located four homicide victims for the FBI in 325 feet (100m) of water in a California reservoir. We have assisted the FBI in other cases and were early responders in the search for space shuttle Columbia debris in Toledo Bend Reservoir in East Texas.

UW: How did you become involved with the Laci Peterson search?
GR: We began working with the Modesto Police Department on this case in early January. We have spent more than 30 days on multiple trips to various locations, with most of that time on San Francisco Bay.

UW: How many people are on your team when you perform a search such as this?
GR: We generally only need a crew of two when we use our own boat and equipment. My wife drives the boat while I operate the sidescan equipment. Occasionally we have one, or at the most two, law enforcement observers onboard. We have found that the fewer people onboard the better. There is less distraction with a smaller crew.

UW: Had you worked with these law enforcement agencies before?
GR: We had not worked with the Modesto Police Department previously, but we have had several occasions to work with the FBI.

UW: When you are called out on a search such as this, how much detail are you given as to what you're looking for? Are you given actual case details, or is it general info like, "female, this height, this weight, etc."?
GR: Generally in homicide investigations, only minimum information is provided initially. As the agency's confidence in us grows and they understand the need for us to have additional details, they will provide more information. The essential information, of course, is height and weight, along with any information about how the victim may be bound or otherwise "packaged." That type of information is critical to visualizing how our target might appear in the sidescan image.

UW: Are you at the mercy of the law enforcement agencies as to where to search and when, or are you consulted as to your recommendations for search areas, depending on the details of the case?
GR: Most of the time the responsible law enforcement agency has very good information regarding the location of the search area based upon the evidence their investigation has developed. Occasionally, we are asked our opinions based upon our experience as well as knowledge of water physics and the inter-relationship between depth, pressure, and temperature as they affect buoyancy of the object we are searching for. In accidental drowning cases, we are given all information available and occasionally we personally interview witnesses, if any. We are also given considerable latitude in evaluating the investigators' information to determine the most probable area to search.

UW: Where specifically did you search for Laci Peterson? Were any of the areas particularly difficult for one reason or another?
GR: We searched beneath several bridges early in the investigation and later focused on San Francisco Bay. The bridges were probably the most challenging since they spanned very deep channels, some up to 325 feet (100m), with steep rocky side slopes. Many of them had tall trees still standing underwater which entangled the towfish.
The major problem associated with San Francisco Bay was the huge size of the search area. Having to deal with commercial ship traffic, in addition to the normal, inquisitive boating public, also presented problems.

UW: How many sites were you able to identify as possibly being Laci Peterson's body?
GR: All I can say is that we were told to expect to find more than what we were looking for, and we did.

UW: What do you look for in the data as telltale signs that you might have found a body? What other objects are most often mistaken for bodies with sonar searches?
GR: Accidental drowning victims are very distinctive and generally quite easy to identify. We can usually see arms, legs, and torso. Homicide victims, however, depending upon how they may be "packaged," are a bit more difficult to identify. Quite often they will not display arms or legs, and may be found lying in a variety of positions because of objects attached to them.
Also, in homicide cases, it is very critical to have an idea of what you are looking for, otherwise, nearly every "out-of-place" object is a potential target of interest.
In another homicide case, an ROV was sent down to recover the victim. The object appeared to be a large boulder in the video from the vehicle, so the ROV operator moved on. After awhile, the agent in charge told the ROV operator to return to the "boulder" and bump into it. It moved - it was not a boulder!

UW: What are the biggest factors in a body search of this type being successful?
GR: Having accurate location information is essential to minimize the search area. Calm water conditions are also a great benefit. Surface wave action from wind or passing boats can cause smearing of the sidescan images and render them worthless. Of course, the bottom conditions are also important. A smooth, clean bottom with no trees, large boulders, or other debris that can hide the object you are looking for is very desirable.

UW: Let's talk about equipment. What exactly did you use on the Laci Peterson search?
GR: We used a customized Marine Sonic Technology sidescan sonar. We have a custom-made stainless steel tow body for the 600 kHz transducer. The towfish is six feet long and weighs about 130 pounds. The extra length makes it more stable and, consequently, the images are better. The heavier weight allows us to work in deeper water with less cable.
This setup requires the use of a powered hoist to deploy the system. Our hoist has a variable speed electric motor with a remote control and is also equipped with a slip clutch to prevent cable breakage if the towfish snags on something underwater. We also used an aluminum tow body for the shallow water in San Francisco Bay. The lighter weight of the aluminum gave us greater layback and tended to somewhat de-couple the towfish from boat pitch and heave due to surface wave action.

UW: Do you use different units for different searches, why or why not?
GR: We use the aluminum tow body when we have to air freight the equipment and use a boat of opportunity. We have lower and higher frequency transducers available for use in searching for larger or smaller objects. The 600 kHz frequency is the best all-around frequency for most of the underwater searches we have conducted.

UW: What have been the biggest advances in underwater bathymetric imaging equipment and software you've seen?
GR: We are actually newcomers to the sidescan sonar business. It was the recent advance in image quality due to the production of higher frequency transducers that really sold us on the sidescan system.

UW: Is it hard for you to separate the horror and humanity involved in body searches such as the Peterson case, and concentrate on the job at hand?
GR: We approach every search with compassion, determination, and the will to succeed. Horrific circumstances cannot be separated or ignored. Often those circumstances instill an even greater desire for success and drive us to work even harder to locate what we have been asked to find.

UW: What's the most interesting or mysterious thing you've ever found, or thought you'd found, underwater?
GR: As for interesting finds, we have had the opportunity to work on Chesapeake Bay on several occasions. We found remnants of at least one unrecorded shipwreck that we reported to local marine archaeologists and are awaiting the outcome of their investigation.
Perhaps the most mysterious object appears to be an ancient dugout canoe that was found in a western lake. We have not had the opportunity to dive on it, but plan to do so.